First off, I'm a huge fan of Ride The Lightning, Master of Puppets, ...And Justice For All (especially this album

), and parts of the Black album. I don't much care for any of their other albums, but damn, 4 killer albums is ok in my book.
But as for the question of whether Metallica has become a "corporation", I don't know. I guess I just don't have enough evidence to say one way or the other whether Metallica has "sold out". Without knowing Metallica's mindset, its hard for me to know whether they are just following the trend or have simply run out of creative energy after 25 years (not too many bands still churn out awesome awesome albums after that long...)
And, for the record, I fully back Metallica's battle against illegal pirating of their music. Personally, I find the idea of copyright protection both insulting and degrading to me as a musican, however, if society sees fit to give musicians economic rights in their music, then they have my full blessing to enforce those rights.
That said, dear god, I seriously hope their future recordings aren't an attempt to "follow the trend". Lol, I'd hate to hear a pop-punk Metallica album (although it would no doubt beat the **** out of Greenday) (Actually, am I the only one that finds it ironic that the popularity of metal has been brought down by the same agressive genre which itself had replaced (punk?))