AFAIK facebook does not allow Ringtone Advertising on their advertising network. But it seems like big publishers still have the chance to advertise with freaking banners on their site. This is a screenshot that I have made on the swiss facebook site. The marked part of the screenshot highlights a "jamba" banner (jamster in english speaking countries) which is obviously advertising ringtones. I'm asking myself how facebook can forbid "normal" advertisers from advertising ringtones, but allow big named publishers to do it? PS: I also wrote about it on my blog.
I just noticed that as well. I suppose with the recent Azoogle lawsuit, they're being more careful as to who they allow to advertise ringtone offers.