two hands at once??

Dear Alois and Jeff 

i see a lot of players on youtube posting a two handed backhand or forehand... is this legal

btw here is a link.. http://www.youtube.com/watch?v=KCw3nZILMGM&feature=related thanks :-) 

Hi Samuel,

As far as I can tell it probably is legal.  It is hard to find anything in the rules that rules it out. 

Sometimes it is referred that the rules talk about your free hand and with a two handed backhand you don't have one.