I’ve had to uninstall RubyAMP, a TextMate bundle that I use several times a day, because it overrode Ctrl+B and refused to let me change it.
I realize most people don’t use these shortcuts, so I’ll explain it. Ctrl+B moves the cursor back one character, the equivalent of the left arrow key without having to move your hands. My workflow uses Ctrl+B so constantly that I couldn’t live with RubyAMP anymore, even though I enjoy its functionality.
The reason this is so negative is the fact that Ctrl+B is not a shortcut that I added; it’s part of OS X. If you are creating keyboard shortcuts for your program or extension, you can’t possibly avoid stepping on every other program’s toes. But the least you can do is avoid stepping on the operating system’s toes. Otherwise it’s just negligent, user-hostile design.