From what I've learned previously, the dudes running Virwox have suits (ie. lawyers) specializing in virtual currencies, and they were around before bitcoin I think. Aren't they big on Linden dollars? So that might be the answer as to why they've been successfull dealing with Paypal for a long time, while small dealers have been quite unsuccesful attempting the same.

But Paypal recently announced some sort of bitcoin integration in their systems, so eventually they might go full blown into bitcoin.

Personally I'd rather see bitcoin take over for Paypal, than to see Paypal embrace bitcoin..