As the legendary Bruce Dickinson said, there is an "unspoken contract between the band and the audience" that creates certain expectations. These same expectations exist in nearly every other facet of life, for better or for worse. You're a novelist-write a novel, not a biography. You're actor-FOR THE LOVE OF CHRIST ACT! You're a conservative-then be conservative. If you're not any of those things, just admit it and everything will be fine.
Apart from media and entertainment, there exists the more crucial (and more common) action of changing belief systems. Like a religious conservative who decides Republicans have been lying this whole time, or a liberal who finally acknowledges the hypocrisy of the party's beliefs.
The idea of selling out applies, much more personally I might add, to everyday life. Friends who you thought genuinely believed in what they said turn out to be attention whores, and politicians you thought held deep principles sold themselves for votes. The person who you thought was kindred spirit, the one who mocked the shallowness of elitist hypocrites but joined them just months later, hasn't matured; he's abandoned his principles. There is a stark difference between admitting, "Dude, I've been wrong this whole time" and simply pretending to never have thought such things.
I truly do respect those who decide they've grown out of their beliefs, whether liberal or conservative, because nothing takes more balls than a deep introspective look at yourself. Even more difficult is the task of coming up with new beliefs, and admitting all the times that you were wrong.
Such was Joe Eszterhas, the famous scriptwriter (Basic Instinct, Flashdance, Jagged Edge and Music Box) and Hollywood playboy, who not only saw the folly in his past, but moved on to a more rewarding future. After realizing the farce and isolated nature of Hollywood, he found religion and moved to what he called "the real America" in Ohio. Not only that, but he campaigned against the immorality and substance abuse that he himself once publicly endorsed. This is something to respect-a far cry from the John Kerry "I voted for it before I was against it" style of finger-to-the-wind politics.
The difference between someone who sold out and someone who has moved on is that one admits it and revels in it, while the other says "I appeared in that acne commercial because I believed in the product, not because I needed some cash." Maturity is self-justifying, meaning that if someone is defending their switch from rock to country, it's probably a move based on reasons other than principle.