What will kill the site exactly? I don't see that many problems with advertisement as a monetization strategy. That has worked well for Google, Facebook, etc.

What will kill the site exactly? I don't see that many problems with advertisement as a monetization strategy. That has worked well for Google, Facebook, etc. I struggle to think of an alternative method of scaling something like this, other than donations (Wikipedia). If you want to target everyone, ads are your best bet. edit: the point is having to log in, rather than the advertisement, that'll kill the site. I'm not sure about that choice either, but similar arguments apply.