I think that what we're seeing is actually just one service being repackaged as many. Echonest provides the data supporting all of these services, so it makes sense that they all look very similar and that there is no remarkable difference in quality from one to the next. However, even with this saturation there actually are a lot of successful music discovery services, so not really a money black hole. http://musicmachinery.com/2012/12/02/music_discovery_is_not_...