imho there is no market for mp3 albums. if such services pick up, they will always encode mp3s at low bitrate (eg. 128kbits if not less) so that it can move fast across the internet, or at least from the legit site's server to the user's computer
in short, record labels will rip you off. they'll charge you say 10$ for an mp3 album and if you want better quality you'll shell out another 15-20$ or so for the CD