Facebook didn't acquire Pieceable, but it did hire the people who worked there.

Now, Pieceable will shut down its Web service that let's people preview iOS apps in a Web browser. It was a popular way for Apple developers to try and show off their iPhone and iPad apps. The Pieceable folks say their tech served up some 800,000 app demos.

Looks like Pieceable's VC, I/O Ventures, is getting hosed in this move. So that it doesn't completely hose its customers, too, Piecable says it will be releasing its software as an open source tool.

To be clear, this isn't a Facebook buyout. "Facebook is not acquiring the company, technology, or customer data," explains the founders on a blog post today.

It's not clear what the Pieceable staff will be doing at Facebook, but given their experience we can make a few good guesses: Helping Facebook build a Web app viewer for its own up-and-coming mobile apps. Or helping Facebook integrate better with iOS. Or just helping Facebook figure out mobile—which it really, really needs to do.