Tracey Chou decides to "Maximize for learning" at Pinterest, not Quora

I remember reading a Quora engineer describing (on Quora of course) his decision making process in joining Quora. A key point in his decision to go with Quora was when Adam D'Angelo told him to "maximize for learning" (or something like that), meaning that he'd learn a lot more at Quora than at the larger more established tech companies that he was also considering. Of course there's a lot to be learnt at Quora and from the great programmers who started it, but at some point the founders are no longer in control of what an engineer can learn at a startup. I was reminded of this when I recently read about the Quora engineer Tracey Chou who defected to Pinterest, which, as everyone knows, is exploding with user growth. When a site takes off like Pinterest is, it presents challenges and opportunities for the engineer that can't be had at another start-up that isn't experiencing similar explosive growth. Most of the foundation work at Quora is in place. It experienced a brief period of rapid user growth but that quickly died off (anyone who uses Quora knows this, in spite of what the founders say) Now it seems like engineers are tweaking little design things (threaded comments, upvotes, ask to answer etc) , but as long as Quora sticks to its core purpose (answering and asking questions) then it doesn't seem like it has a lot to teach an engineer after they've learned the initial set up. Quora lost an engineer (Tracey Chou to Pinterest) and also recently gained a couple new hires. As TechCrunch explains (http://techcrunch.com/2011/11/23/quora-gains-a-twitterfacebook-growth-expert-loses-top-engineer-to-pinterest/), both of those new hires were brought in to focus on, what else, user growth. Pinterest has it (and snagged an engineer because of it) and Quora is trying to manufacture it by bringing on some new hires to focus on it. But can you manufacture user growth? At some point it all boils down to how popular the underlying idea is, and Quora's isn't really that popular. It's most active user is one of its own hires (Marc Bodnick) who seems to spend all his time voting up other people's answers to encourage site participation. Quora is paying for its own user growth, while Pinterest's is happening in spite of itself (Pinterest is still in Beta and requires an invite) Quora will probably get a lot of traffic in the future as people search for information, but in terms of having a really large number of active users...meh. Pinterest meanwhile ...that's a site with potential.