On New Media Age (sub. req.) Sean Hargreave explores the state of the art of advertising on instant messaging services such as MSN or Yahoo! Messenger. If you want to target teenagers this seems to be the perfect channel to use. It's not just about placing a banner at the bottom of the application, but most of all about creating "skins" or branded theme packs to personalize the IM interface.
One interesting example of IM brand campaign comes from French Connection gave users of Yahoo! Messenger the possibility to browse FCUK 2005 collection and try on the latest fashions by customising their Yahoo! avatar or virtual identity.