http://www.baekdal.com/opinion/piracy-or-not
I agree with most of this.
I also feel that all games should have an available demo. I can't count the number of times games have been hyped up, trailers have been grossly exaggerated, I pre-ordered the game and they bombed! I wasted 50-60 dollars on a game that was misadvertised and since the keycode was now used, it's unsellable. I could sell the account but that's technically illegal because even though you paid for the game and have rights to your account, it's technically not yours.
Also, there's some great software out there that comes with a trial version but have severe limitations on top of the 7-30 day trial period. This limits the possibility of gaining knowledge by self-teaching yourself how to use the software AND doesn't give you an accurate taste of it's capabilities or learning scale. Do I really want to pay $500 dollars for something that may be extremely hard to learn just for learning sake? Probably not... but if the trial gave me full access I could get a taste and if the time came where the software was needed, one wouldn't be completely in the dark about what they're getting in to.