Pinterest took a key step to transform itself from a social phenomenon into a real business.

It hired Tim Kendall, formerly of Facebook, to figure out how to monetize its rapidly growing users base, Fortune reports in a big profile of the upstart social network.

Kendall worked at Facebook from 2006 to 2010 where he was director of monetization. When he left Facebook, David Fischer, VP of advertising and global operations, wrote a glowing memo about Kendall's contributions to the company:

Over more than four years at Facebook, Tim has had an incredible impact on the company, and in particular on the development of the ads business. Starting back in 2006, Tim wrote the blueprint for our monetization strategy. (You might be wondering how I know this given I haven’t been here that long, but trust me on this — Tim gave me a copy of the document when I started and strongly “advised” me to read it. It was good advice.). In all seriousness, it is safe to say we would not be where we are today without Tim.

Tim recognized early on not only that advertising could be social, but that it should be social on Facebook. What began as “sponsored stories,” social advertising has transformed the marketing business. And again, Facebook has Tim to thank.

At the time of his departure from Facebook, Michael Arrington of TechCrunch wrote Zynga and Twitter were trying to hire Kendall. He didn't go work for those companies.

Instead he's at Pinterest where he will have to figure out how to convert all those engaged users into real dollars.