Hence the evolution of music...I personally have got to respect someone who stands for what they believe in (at any cost) yet at the same time, money = success in the public eye. It's really a personal decision to stand on what you believe -vs- "selling out". I've always had a problem with those words - "selling out", making a decision to forget what you grew up with and going to whats popular isn't "selling out" to me. It's evolution, it's exploring new areas, it's opening new doors.
Alot of people say that Kanye sold out, Timberland sold out, Jay Z and so on...I view what they did as making a change to make more money. To get the money, they had to venture in other directions but keep hip hop essentials in their music. The idea is to be successful in both worlds. So to me, it's not really "selling out" but going for more success. I don't think we should view them as two different things anymore, hip hop has always been about making something from nothing. In the beginning hip hop didn't have access to the pop crowd, these cats have only opened that door for hip hop to grow. Now we have to decide to either walk through it or stay on one side of it but it's not "selling out" (imo).