My veiw of alignment is as follows:

I get all my players to create a character with and have a good idea of what that character is like as a person but with only a rough idea of what the characters alignment is based on the characters personality. By the end of say, session five, I'll have a quick chat with the player and we'll agree an alignment since, in game terms at least, you do need an alignment for spell effefcts et. al. I've never questioned a players decision based upon their alignment but acting severely out of character draws the attention of both the players and the DM. For short games it's a decent enough way to lossely describe a character that only needs an outline but for longer campaign play I personally find it too limited in scope to be of any real roleplaying value. Just my 2 Cents feel to disagree