Powerbombs aren't Banned. You do know that 'Tista's & JBL's finishers (atleast one of them) are both Powerbombs.
As for the Piledriver, same thing applies that dude just said above, if the wrestlers knew how to do them properly then the risk of injury would be slim to none. Though, it's very easy for someone to fuck up a Piledriver and for that reason it's been banned. Though, the German has a far less likely chance of injury compared to the Piledriver because with the German, your intended to land on your Shoulder Blades as opposed to "landing" on your head with the PD.
As for moves not being outlawed in TNA when they are in WWE, alot of it has to do with Vince being a smart business man. You know how devistating it would be to have a Rock or Triple H suddenly be sidelined because someone botched a move that's risky to begin with? It could be devistating to the ratings, to business as usual and overall, devistating to Vince's pockets.
Though, I'm sure there is some concern for the wrestlers in Vince's decision to ban certain moves. Though, I do agree that it's gone too far, look at the Cruiserweights... they are highly restricted in what they can do on the top rope.
Then again, Vince fucked up the "Cruiserweight" Division a LONG time ago. You remember back to the Cruiser matches from WCW... they were fast paced, lots of reversals and overall contrasted with the "Normal" wrestling very well for a great affect. Vince's vision of "Cruiserweights" is no different then the "Light Heavyweight" division of old. He seriously needs to let the Cruisers go in the ring and let them do what they do best.
