Last week, StumbleUpon announced it was buying itself out of its much-vaunted previous corporate buyout, by being born again as an “investor-baked start-up.”

The Canadian-born social-bookmarking company, which was launched earlier, had come to the Bay area in 2006 and got some fancy angel investors, who ponied up a couple of million dollars. It soon became a traffic-generating hit.

Then, StumbleUpon was bought by eBay (EBAY) two years ago for $75 million in one of Web 2.0’s high points.

End of a fairy tale? Um, nope.

Soon enough, due to both buyers’ and sellers’ remorse, rumors of the San Francisco-based company being sold by its new owners swirled around it, although there was no sale.

Instead, last week, StumbleUpon announced that a roster of well-known Silicon Valley investors, including Ram Shriram of Sherpalo Ventures, Accel Partners and August Capital, would return it to its roots.

Its founders, Garrett Camp and Geoff Smith were included, with Camp as CEO.

In a video interview he did with BoomTown, here’s Camp talking all about the latest shift for his start-up, including discussing some more changes on the site, such as an even more personalized Webification of the content discovery service.

Here’s the video:

The content-discovery service, StumbleUpon, has gotten itself back to start-up status, after being bought by eBay two years ago.

It announced today that it was returning to being an “investor-backed startup” by a roster of well-known Silicon Valley investors, including Ram Shriram of Sherpalo Ventures, Accel Partners and August Capital.

Its founders, Garrett Camp and Geoff Smith are also back, with Camp now in place as CEO.

“We are grateful to eBay for its guidance. However, we realized there were few long-term synergies between the two businesses. It is best for us to part ways and focus on our respective strengths,” said Camp, stating the very obvious.

That’s quite a boomerang since it was acquired by the auction giant in 2007 for $75 million.

Before that event, which was at the height of the Web 2.0 fervor, the Canadian-born social-bookmarking start-up, which launched several years ago, came to the Bay area in 2006 and got some fancy venture investors (Mitch Kapor, Ron Conway, Shriram and others) who ponied up a couple of million dollars. It soon became a traffic-generating hit.

But rumors of the San Francisco-based company being sold by eBay (EBAY) have swirled around it almost since it was bought, although there was no sale.

The same has been true for eBay’s other purchase, of voice-over-IP service Skype. A recent report in the New York Times said its founders were also considering buying Skype back from eBay.

Under eBay, the site has floundered a little bit, but made some changes, such as unveiling a new Web-centric look and feel and a new partnering program last fall that represented a major shift for the online discovery service.

In that change, users no longer had to register for the service or download its toolbar to “stumble” the Web.

Terms of the deal were not released, but we’re digging! Um, stumbling!

More to come, but here’s the full press release from the company, as well as a video I did at the party StumbleUpon threw after getting acquired by eBay, including an interview with then-thrilled Camp:

StumbleUpon Goes Independent; Backed by Founders and New Investors

April 13, 2009 – StumbleUpon, the best way to discover new content on the Internet, today announced that after nearly 2 years as a subsidiary of eBay Inc., it has returned to the ranks of an investor-backed startup. StumbleUpon is now backed by the original company founders, Garrett Camp and Geoff Smith, as well as a number of well-known investors including Ram Shriram of Sherpalo Ventures, Accel Partners, and August Capital. Camp takes on the role of CEO of StumbleUpon.

“We are grateful to eBay for its guidance. However, we realized there were few long-term synergies between the two businesses. It is best for us to part ways and focus on our respective strengths,” said Camp. “This change makes it possible for StumbleUpon to continue to innovate and focus on becoming the Web’s largest recommendation service.”

“StumbleUpon helps users discover the best of the web–it’s a way to find interesting content you wouldn’t think to search for,” said Shriram. “StumbleUpon’s personalized recommendation engine brings serendipity back to websurfing, and lets users sift through socially-endorsed content with a single click.”

StumbleUpon will remain focused on helping people discover interesting content by increasing the accessibility of the StumbleUpon service and the quality of recommendations. In addition, StumbleUpon has plans for several new products and features to be released in the upcoming months.

While rumors of its impending re-sale have apparently been greatly exaggerated, what’s true about StumbleUpon is that its new Web-centric look and feel and a new partnering program represent a major shift for the online discovery service.

The San Francisco-based company, which was founded in 2001 and sold to eBay last year for $75 million, is announcing tonight that users will no longer have to register or download its toolbar to “stumble” the Web.

Users can now simply start on StumbleUpon’s site, for example, and stumble all over the Web using their Web browser as guide rather than a toolbar.

The move is being made simply because most Internet users are increasingly loath to install Web plug-ins like toolbars, a requirement that naturally has slowed the growth of StumbleUpon’s service over time.

Currently, StumbleUpon has about six million registered users, although only a fraction of those are responsible for the approximately 12 million daily “stumbles,” all using a toolbar.

“We wanted to attract users who do not want to use a toolbar, making it easy so they could use the service right from the get-go,” said Garrett Camp, co-founder of StumbleUpon, in an interview with BoomTown earlier today.

Camp noted that that the toolbar–which has been downloaded between 11 and 12 million times–has seen that growth slow over time. Nonetheless, it is not being eliminated either.

“[Toolbar adoption] was still growing, but not accelerating,” said Camp. “Being able to stumble without one was the biggest feedback we got from users.”

Along with the Web-stumble change, StumbleUpon is also unveiling a redesigned homepage–see an example of it below; click on the image to make it larger–which is an attempt to make it more of a destination.

With the new look, visitors can find content by topic and more related to interests. Other changes include a new look for profile pages, as well as user reviews, rating and comments.

Along with its distribution shift and site renovation, StumbleUpon is unveiling a partner program called StumbleThru that will allow visitors to discover content within those sites without going to StumbleUpon.

Sites–starting with HowStuffWorks.com and the HuffingtonPost.com and followed within weeks by RollingStone.com and National Geographic–will display a StumbleUpon “badge” or custom widget.

It is not unlike similar buttons that now dot Web pages from news discovery services like Digg, which users can click to find related pages.

Essentially, much as Google (GOOG) delivers custom search within Web sites, StumbleUpon is offering custom surfing, giving publishers StumbleUpon technology to allow its users to surface content within their sites that is often deeply buried.

As to the blog reports that eBay (EBAY) had put StumbleUpon up for sale after owning it for a little more than a year, Camp essentially dismissed them, noting that the unit is still operating as an independent subsidiary of the auction giant.

“They have given us a lot of runway,” said Camp.

Here is the new front page of StumbleUpon:

Also, here is a video I did last year at the exceptionally noisy (sorry!) party that StumbleUpon threw after it was sold to eBay a little more than a year ago: