[Lil' Lavery]

It all depends on the ramp and how it is used. Some ramps are great defensive tools, and do help center of gravity, but some are excessive or prove to be a tipping hazard. While Im sure 233's sloped edges were made for defense, I saw them once push another robot down, and heard they did at least one other time. Im not sure if they would have tipped these robot's anyway, but the ramps looked to be a very definate help to the tipping. Im also positive that they werent used intentionally. The tip I saw was during autonomous and of their own teammate.
Ramps that prove to be dangerous over the course of competition should be adressed, but not all ramps. If a team developes a record of using the ramp aggressively or of its ramp flipping other robots on several occasions that team should be instructed to do something about the ramp.
While ramps are often the simplest solution to opposing "bricks" and CG issues, their are countless others. Outriggers dont have to be ramps. in 2004 we had a "wheelie bar" that prevented us from tipping while climbing onto the platform to hang. This year Team 118 had small PVC tubes that curved down to the floor (they started parallel to the floor, and curved until they were perpendicular, so they couldnt be a ramp nor ramming spikes) that helped keep them from tipping. Also, our drive system this year was fantastic from keeping us from tipping.
For those who havnt seen it, it is a holonomic drive system, but instead of the wheels being mounted vertically along the 4 faces of the robot, they are mounted on a 20 degree angle in the 4 corners, allowing our "footprint" or Conservative Support Polygon to be as large as possible, as well as lowering the drive systems CG. Because of that, we never even came close to tipping. Also, by avoiding massive, heavy arms, ect. you significantly lower your CG.
As for defense against brick bots, there are a number of bumper designs that can beat them. Also, just having a faster, more maneuverable, or stronger robot will often do the trick. "Cattle plows" or designs that drive with a leading corner will also usually deflect the blow. Outriggers, or some form of device to "plant" you to the ground can be highly effective for holding ground against powerful bots as well (like the top of the ramp in stack attack, or the top platform last year). High traction drive systems, like many tank treads, can do a great deal to hinder bricks as well.