Examples of when it is not advantageous to be lightweight

[Travis Schuh]

I think your implicit assumption is that being lighter gives you a more maneuverable robot by decreasing acceleration time.

If your goal is to make your robot more maneuverable, then I could see taking weight out of your robot at the cost of raising your CG above an acceptable height resulting in a net decrease in maneuverability. If there is no option to lower CG through re-arranging components, then it may make sense to ballast the robot. It also helps if the CG is closer to the center of the robot for best handling. I think for these reasons contributed to 254 ballasting their robot this year.

There are plenty of matches where teams either outright tipped or had to drive cautiously because they were tippy (you asked for specific matches, I would say watch some of 973's 2013 matches). I bet many of these teams would have added ballast if they had weight.