A couple of weeks back I read in Martín Varsavsky's blog about Blyk, a mobile operator targeted to teens that is wholly funded by advertising.  Interestingly enough, some former Nokia employees are in tops spots at the venture, such as Pekka Ala-Pietilä.

They're starting out in the UK, but will move over to other European markets soon.  This is surely a development worth follow-up.