[rhizome]

I don't use FB apps, but by any chance is it common to provide rewards to users for inviting their friends via Requests?

[misnome]

Yes, at least if not directly - then by making it harder to proceed without "friends" playing the games.

Also, it's not like they have carefully selected the group of friends that they want! The ones I have seen just have a "Send to all friends" tickbox.

[makomk]

It's still allowed for games, though.

[idoh]

The fb policy is that you aren't allowed to incentivize the sending of requests, but you can give a reward for someone accepting a request. A subtle distinction, but a distinction nonetheless.