PayPal does actually have a policy on this somewhere, which I have seen recently but can't remember where. There is some specific number of days between payment and delivery that is acceptable to PayPal, but I think it's quite a lot. Also, PayPal themselves sometimes hold a payment for 21 days.

And by the way, MtGox imposed the 30-day waiting period for everyone, not just on transactions that it suspects may be fraudulent.

I'm leaving this thread now, because I don't speak for PayPal or for MtGox, but I hope you won't try to pressure MtGox into reversing trades that other people carried out with you in good faith. That would be tres uncool.