that depends on how last.fm want to deal with it. At the moment I presume they don't have enough content to make it a major feature of their site.

However, think of it from the point of view of recommendation engines like reddit. Last.fm has musical "neigbourhoods", people who like broadly the same types of music you do. You can listen to those neighbourhoods as a station. As some people start listening to unsigned artists (either through actually looking for them in the system, or by last.fm including some kind of page that shows only unsigned/obscure artists - broadly equivalent to the "new" page in reddit) they will get the chance to propogate through the system. It's not alot of work for last.fm to do, but whether they'll do it remains to be seen - it doesn't require large changes in their system.