[Lil' Lavery]

I will have to disagree with you here Katy.
Bumpers most definitely aid in preventing robot damage. It's clear even from just looking at robots with bumpers in 2006/2007 against those without. In a PRACTICE MATCH in 2006, 116 fielded our robot without bumpers (because we had them removed to work on the robot earlier). We left the field with a 1" dent in our box channel frame. In 2007 we added bumpers, and despite being the focus of much more defense than in 2006, we suffered no damage to our frame. Parts of the robot not covered by bumpers (such as our "hood") were significant dented.
The team I now mentor, 1712, didn't use bumpers in 2007. The '07 bot has significant denting to the corners of the frame that was already present after only one regional. I also noticed a much higher incidence of items such as wire ties breaking or bots coming loose while working with them at off-season competitions than was true with 116 during 2007.
Claiming that having a mandatory weight placed lower on the bot waters down engineering is questionable at best. It's still quite a challenge to deal with creating a robot to interact with tall field elements and game pieces in such a high pace environment, with or without the bumpers. Many smart teams would be adding optional bumpers (per rules of previous few years) to deal with this scenario anyway.
I've also seen definite proof that bumpers can aid with tipping, as their geometry often has them act as "wheelie bars" for teams slowly tipping over. In more than once instance I've seen team balance on their frame and bumpers while pushed against the Rack or Overpass.
Aggressive driving has existed since well before mandatory or even optional bumpers rules, and I really don't think drivers play more aggressively with or without them (ever watch the 2002 and 2003 games?).
After the 2006 game, I really don't want any team I'm involved with to field a bot without bumpers. I've seen first-hand the damage that can be caused by harsh defense and metal-on-metal contact. I've seen bots who have a 1" steel pipe serving as their "leading edge". I don't want that smacking directly into my robot at even mild speeds.