My understanding is that the GPL doesn't have fucktons of precedent behind it in court. You bet the house on a big case and lose, the precedent will stick with GPL and may even weaken all copyleft licenses.

Also, it's better to gently apply pressure and set a track record of violators taking corrective measures so when you end up in court one day you've got a list of people and corporate entities which do comply because they believed that the terms were clear enough, which would lend weight to your argument.

Saying this as a GPL hardliner myself.