It used to be, before this whole iTunes thing, Bands would compete against each other to see who could sell the most albums, that doesn't exist, now we can just go onto the perthetic apple iTunes and download just the few songs from that album that we like, therefore the album selling rate on bands has decreased. Although it does make newish bands get fans and what not quicker, but its just my opinion, i believe its destroying music
If you're talking about ruining the financial state of the artist/band then yes, quite obviously artists/bands aren't going to receive as many funds as they get from tours and records, even though such costs as the value production, the cost of the packaging, the record company taking their share of the material, then yes it is. But to say that it's ruining the quality of the actual music produced? No. Bands and artists are still able to create their desired material. Granted, a lot of artists hate it, but it isn't lessening the quality of the material.
Music cannot be ruined by a source of purchase. Saying that iTunes is ruining music is like saying that your favorite music store is ruining the musicality of an artist. But if the statement is talking about the profit of an artist, it still doesn't make sense because Beyonce in particular released an album very recently without any promotion on quietly put it on the iTunes store. Beyonce made a lot of money. One still requires to buy and use actual money in the iTunes store. ITunes does not ruin the financial motivation of an artist since they can still get money.