I understand, and I don't want to use the excuse "everyone else is doing it" but instead I like to think of using songs that some people may not heard of as free advertising for the song.
I had people PM and ask me where they could get those songs, and I pointed them to Amazon.com, Itunes, etc. and made a sale.
If I heard a song I did not have, that was used in a video, I am inclined to buy the song, if I like it.
I know the law is the law, but the law can be a fool.
I'd rather have a high quality version of the song, instead of the reduced quality versions on youtube.