I rep for good posts, for good points made in posts, whether I agree with them or not. I rep if you make me laugh, sometimes a sense of humor is too rare. I will rep anyone with whom I have enjoyed the exchange of ideas, whether I agree with their point of view or not. I have been know to rep for Jimmy Buffett references...go figure...
I have never and will never give a neg rep. Just as I believe personal attacks are a sign someone has gotten under your skin, so goes the neg rep.
As some have noticed, I always try to send a thank you message for positive reps. My feeling is, if you can take the time to tell me you liked my post, I can certainly take the time and be polite to say "thank you." I do not expect the same, I do it simply because that's the way I am.
"I am allergic to piety, it makes me break out in rash judgements." - Penn Jillette
"I have never killed a man, but I have read many obituaries with a lot of pleasure." - Clarence Darrow
"The man who invented the telescope found out more about heaven than the closed eyes of prayer ever discovered." - Robert G. Ingersoll