Not really, a label does much more than get an artists music in a store. Distributing the content is probably the easiest thing for artists to do on their own. Marketing, touring and merchandise are more complication and labels are still the best solution.
Well, that's why I said "take" on it. These companies are actually doing quite a bit that a traditional label would do: they store the media (the digital version of manufacturing it), distribute it, and market it. I don't think a traditional label is always the best solution, especially for groups that will never be big enough to justify the huge upfront costs a label puts in.
These aggregators are really for the tail end of the spectrum: the 90% of bands who represent 1% of music listening time and don't have much hope of getting signed.
