Look at this guy on here, calling everyone douchebags and idiots. First off, tipping debates aside, dealers are not the most important person to have on your side. For counters, sure, a dealer can tip off the pit. Big deal! If the dealer can make the play, so can the pit. Play a different shift, play a different casino, whatever. If you tip (and I like to tip dealers with pleasant attitudes, and no, I don't tip away my EV), make sure you're tipping only a portion of your EV that you're comfortable with. It's very easy to erase your edge by tipping, but that doesn't mean you have to be a stiff.
For players that have a bigger edge and can afford more tipping (if desired), you have even less to worry about from the almighty dealer. Why? Because if they could make your play, you wouldn't be playing with them! In other words, if they were able to make the play and the conditions remained the same, potential collusion becomes a factor and you shouldn't be playing there anyway. If the conditions remain the same, it's usually because the dealer doesn't know your strategy.
Personally, I treat tipping as a business expense. If a dealer is nice and pleasant to play with, I want to show my gratitude; I want to keep them happy. I generally don't tip unpleasant dealers unless I have a very good reason to do so. But remember, tipping only goes so far with dealers, and they're not as powerful an adversary to the AP as some of them think they are.