Do the Debian legal people annoy you? Then why not release your software unlicensed; they won't be 'able' to use it and other users who care less will. Ah, but that isn't much fun... why not rile them up as well? Enter the "do no evil" clause! By being 'open source' in such a way that they cannot use their software, you can apparently cause a decent amount of grief.
They also seem to be good for getting amusing quips like "IBM requested an exception so that they can do evil with my software".
Do no evil clauses are great for trolling. An anti-corporate and anti-'takes-themselves-seriously' license.
Hardly even a use of the legal system, the clause would not stand up for one second. What is really being used is the victims attitudes toward the legal system.
It sort of seems like this license may bother you. It really is good at this.
So did we, because it's not really open source, and most distributions won't accept stuff that uses it (fedora, debian, etc).
Thus, if you want to use it in anything open source that you actually want packaged, you need an exception.
I have trouble seeing anyone, anywhere, ever, enforcing it.