Even though Jupiter Research saw that ringbacks aren't popular in the US, Cingular throws down the mobile phone gauntlet (do they have Gauntlet for mobiles? I'd definitely play that) and declares that ringbacks are available NOW.

For the uninitiated, ringbacks are what people hear when they call you, as opposed to ringtones, which is what you hear your phone play when people call you. Cingular's calling these "Answer Tones", and cost you $1.99 each, and $0.99 a month afterwards. Maybe if they were a bit cheaper people would like them more. – Jason Chen

Cingular Answer Tones [via Mobile Tracker]