Bands, game creators, and other producers of media can all be sell outs and deserve to be despised for it. Sadly there is little you can do to someone who sells out without breaking the law.
Some people here seem to misunderstand what it's about entirely. It's not about being "indie" so much as giving up ideals and stabbing a fan base in the back. Basically bands, writers, game creators, are fine when they create a decent product, typically doing what they want to do, and make a decent profit doing it. Things change when someone notices that this creator (of any sort) is doing pretty well but figures with a lot of changes they can make a lot more money. A "sell out" happens in music when some new agent or big music company comes along and tells an artist they can make unheard of tons of money by changing around what they are doing and using their moderate success as a springboard. Usually the deal is the artist does what the agent tells them, and then they wind up splitting the profits. As a result the artist with their name out there gives up what they had been producing to do mainstream stuff, changing most of the stuff that made them great to their initial fans, and makes tons and tons of money. The idea being that even if everyone eventually wins up hating them, it doesn't matter because they have tons of cash.
The thing is that most bands that are accused of selling out aren't usually obscure. They are known, which is why they have the option to begin with. This is why a lot of indie music fans fear bands being recognized on a large scale due to that being when they inevitably receive (and take) the offer to sell out, which amounts to them making everything they do palatable for the widest group of people possible, and removing anything from their act that pushes the envelop outside of accepted parameters.
There is the endless question here as to whether bands, or other producers of media (which have tgheir own versions of things) owe their fans anything. Typically a sell out will say "no", but in reality they do. See, without the support of the fan base they betray in these cases they never would have become popular enough to be in the position to sell out to begin with. All those guys who bent over backwards to attend a show when a band due to what it did, and what it stood for, so it could succeed and stay in business are justified in feeling betrayed when a band basically takes a leak all over them.
Some people here are pretty honest though, saying that they would gladly sell out for "F@ck You" money, and that in of itself is the problem, most people will.
When it comes to video games, you see it in terms of a game developer that builds fame and fortune as a developer of single player RPGs, selling out to make shooters, or social games, becuse that's where the money is. Without the support of the RPG players they never would have been in a position to even consider such a transition, and refusing to cater to the people that made them, especially when they started up, is a betrayal.
It's important to understand something here. People usually don't start screaming "sell out" when someone changes to genuinely survive. It's when it happens to maximize profits. When a band is called a "sell out" they are usually making pretty good money, enough to definatly support themselves, it's when they decide they want 10s of millions of dollars that there is a problem. The same applies to gaming (which I bring up as a parallel so often here because this is a games sight) when a company say decides to chase apps or the casual bandwagon, because it's done to maximize growth and profit, not out of nessecity. Epic length single player RPGs will support a company just fine, but you don't see many of them because there is a lot more potential profit to be made by grinding out casual software like apps, social games, and similar. Likewise you see MMOs like "The Secret World" and "The Old Republic" being touted as failures, and pointed to as the whole type of game being unworthy not because they aren't making money and won't generate a long term profit, but because more money can be made faster by designing smaller, free to play games from the outset.
At any rate Linkin Park is a huge sell out here (though I'd argue they sold out long before now, but that's another discussion) because getting in bed with a big company for an "of the moment" shooter game is exactly the kind of thing they were not supposed to do, it's the opposite of everything they said they stood for both in person, and in their music. Linkin Park is making decent money, it doesn't need these revenues to survive or anything (and in their case they should be willing to die before they'd take money for this), it's all about lining their pockets with more millions.
That said, I like a lot of what Linkin Park did, and have always admitted that. I've never been fond of Nickelback though, and could never figure out why anyone bothers to either love or hate them, they seem kind of mediocre overall. I guess that might be the point though, they seemed like they were a product to begin with and were never their own people to sell out to begin with, a product intended to be mainstream through and through, the "edgy" nature of their work when they try to put it in, being "edgy" in the way that isn't going to get anyone in trouble or be all that contreversial. In comparison Linkin Park has been calle depressing and skirted contreversy in the past, with people trying to tie them to teen suicides and such if I remember. I missed it if it happened, probably from not caring, but I don't think Nickelback has ever raised many eyebrows or gotten any kind of attention despite the kind of music they are trying to play.... which pretty much makes them more of a product than a band that later becomes a product.