Facebook has a no-refund advertising policy so they can cancel ads without a warning. They also don't say what kind of ads are or aren't permitted.
I emailed them on the 12th to inquire about advertising a poker site.
[Thu Jan 12 20:49:40 2006]:
>
> Am I allowed to advertise a poker site?
>
> Let me know, thanks.
>
> Jay
Here is their reply today, 8 days later:
No, if we catch you doing it, we'll disable you from our site.
Consider this a warning.
Areg
Consider this a warning? Anyways, don't bother advertising there.

They won't say anything about poker sites, because they want you to pay first.