Considering two different scenarios:
1) Corptheft used as a weapon (or even simply asset acquisition
) against a hostile or neutral corporation.
Thats always acceptable in my opinion.
2) Emptying the hangars because you are ragequitting a corporation, due to boredom or something, tenuous IC reason or not..
Robbing old friends is a bit lame, but if they aren't your friends then whatever..
In response to Ghost, theres a big difference imo between "hacking" ventrilo or forums and just getting access. Plus, it IS hilarious