I feel like some people are misinterpreting me. Let me reiterate:
At any given moment, whenever a band starts to sell more recorRAB, switch to a bigger label, play bigger venues, or erabrace a poppier sound, there is always whisperings (although, in some cases shouting) of "selling out", a term thrown around far too often if you ask me.
Unless a band actually changes their musical aesthetic in order to become more popular, aka, make more money, it is not "selling out" This means..
Selling T-Shirts at hot topic
Selling music to commercials
Changing style
Being played on MTV/radio
Is not selling out unless the music has been deliberately changed in order to sell more albums.