While onlookers have always been puzzled about why eBay bought Skype, an even more bizarre acquisition by the online auction giant, though on a smaller scale, was that of StumbleUpon, back in 2007 for a reported $75 million.

Today, the mismatch has apparently been dissolved, with StumbleUpon announcing that it has “returned to the ranks of an investor-backed startup” according to a press release and investor David Hornik.

The move comes at an interesting time for StumbleUpon, as it faces serious competition from Digg, who now has Stumble-like features in the controversial DiggBar. The company has been doing some exciting things though recently, including its Premiere Partner program for Web publishers (of which Mashable is a member).

Hopefully, freed from the bureaucracy of an Internet giant like eBay, StumbleUpon will become a more nimble startup and keep the innovation going. This is essentially what StumbleUpon founder Garrett Camp – who is using some of his own funds to free the company from eBay – suggests, saying, “This change makes it possible for StumbleUpon to continue to innovate and focus on becoming the Web’s largest recommendation service.”

Meanwhile, this could be the first step of eBay dissolving what has essentially become a holding company for a number of startups that don’t really fit into its main auction business. Speculation continues to mount that the company will soon spin-off or sell back Skype to some of its original investors, in a similar deal to what was just announced with StumbleUpon.

See Also: HOW TO: Get the Most Out of StumbleUpon