Since you're sporting a Metallica avatar, let's talk about them. 
Was Metallica a sellout for their eponymous fifth album? A lot of fans seem to think so, and it seems apparent that there's a couple of tracks on that album ("Enter Sandman" and "Nothing Else Matters") that are intended for broad appeal and FM airplay, the album certainly did enjoy broader appeal, and a one or more other tracks got airplay as a result. Is the rest of the album that big of a departure from "...and Justice For All"? I don't think so.
It's pretty apparent that from covers that they've recorded that they're interested in playing a broad range of music. I mean it's no surprise when they cover Diamond Head, Misfits, Mercyful Fate, and Motorhead - but covering Bob Seger, Lynryd Skynyrd, Queen, and Blue Oyster Cult is indicative of a broader musical range.
That to me is reinforced by Load / Reload, two albums that were not particularly popular with long-time fans, and were not nearly as commericially successful. If they were sellouts, they did not sell well. I don't think anyone could call "St. Anger" a sellout and keep a straight face. You could say it sucked, and I would disagree, but that's a subjective judgment.
In short, a band's musical interest may change (and may even be wholly motivated by money - I'm looking at you, Kiss), but the fanboy's doesn't seem to.

Was Metallica a sellout for their eponymous fifth album? A lot of fans seem to think so, and it seems apparent that there's a couple of tracks on that album ("Enter Sandman" and "Nothing Else Matters") that are intended for broad appeal and FM airplay, the album certainly did enjoy broader appeal, and a one or more other tracks got airplay as a result. Is the rest of the album that big of a departure from "...and Justice For All"? I don't think so.
It's pretty apparent that from covers that they've recorded that they're interested in playing a broad range of music. I mean it's no surprise when they cover Diamond Head, Misfits, Mercyful Fate, and Motorhead - but covering Bob Seger, Lynryd Skynyrd, Queen, and Blue Oyster Cult is indicative of a broader musical range.
That to me is reinforced by Load / Reload, two albums that were not particularly popular with long-time fans, and were not nearly as commericially successful. If they were sellouts, they did not sell well. I don't think anyone could call "St. Anger" a sellout and keep a straight face. You could say it sucked, and I would disagree, but that's a subjective judgment.
In short, a band's musical interest may change (and may even be wholly motivated by money - I'm looking at you, Kiss), but the fanboy's doesn't seem to.