[palehose]

Every comment submitted here is kept by Y Combinator and they own it in the same way facebook or "applebook" would own it, except they don't run ads. But if you were to apply to their accelerator they would use your comments to determine if they want to accept your business idea so there is definitely added value to them of your data being surrendered to them freely.

[icebraining]

They do run (job) ads for YC companies, there's one in the front page right now.

[the_watcher]

You don't have to tell them your handle. They ask for it if you'd like, but they'd be bad investors if they declined applications from people who said something like "I'm a lurker and don't have an account"