Whilst I tend to stick to emusic as my source for music I recently took the plunge with mp3fiesta since besides emusic it seemed to be able to fill the gap for the more obscure albums I was after - however I haev noticed that they have more than back catalog stuff which made me a little suspicious at the prices they charge.
Of course I did 'check them out' and their ecommerce credentials are impeccable - unfortunately a google search suggested that they were good boys, subsequent searches have shown me that they're acually a russian outfit mostly posting stuff they've scraped from torrents or elsewhere (hence the variety of bitrates etc). So once my current balance is out I'll not be using them as clearly they do not in any way support artists/labels (I thought the latter since it seemed back-catalogue stuff to me) and they basically just recycle stuff you can get for free anyway.
As for tagging stuff as available from them - I shall carry on as my intention here is to find the best source of mp3s on the web and if it happens to be a site in Russia (that is legal under Russian law) well that says more about the record industry's failure to get stuff out there and create mp3 portals where you get can just about anything you ever want. I mean if I was a seller I'd take requests (I mean once burnt you can resell ad infinitum and data on what's being requested would informa marketing decisions add infinitum).
My big debate now is whether I should make a concerted effort of tagging torrents (where available) and iTunes (which I just plain don't like) to see how good as sources they are too.
Please feel free to comment on this one...