Online radio service Last.fm has always seemed to occupy an awkward middle ground between on-demand streaming music services that let you pick and play any song--like free services Imeem and Grooveshark, and Rhapsody, which charges for its service--and the radio-to-your-taste service pioneered by Pandora.

In my opinion, this is partly because of some flaws with the service itself. The radio service has a lot of powerful features for serious music fans who are willing to do a little work, as CNET's Donald Bell recently explained, but it doesn't work very well as an on-demand service. How do you add songs to a now-playing queue? Why hasn't Last.fm secured on-demand rights for huge artists like Pink Floyd and Led Zeppelin?

More: http://news.cnet.com/8301-13526_3-10351788-27.html