In 2012 wsop rules pdf file, I couldn't find any information about trash talking. Is it legal or illegal in world series of poker? From 2006, I find a video called Jamie Gold talking with trash talk but I don't think that was a trash talking.
As This article explains -and I remember watching Negreanu complaining about it on the feature table of 2011 WSOP Main Event- there is a rule that almost forbids all talking on the table.
"41. No Disclosure
Players are obligated to protect the other players in the tournament at all times. Therefore, players, whether in the hand or not, may not:
- Disclose contents of live or folded hands,
- Advise or criticize play at any time,
- Read a hand that hasn't been tabled.
The one-player-to-a-hand rule will be enforced."
Specially number two leaves trash talking out. The article points out it's a seven years old rule, but it has been really enforced on last year WSOP. It's my understanding that on this year WSOP (2012) that enforcement has been relaxed a little, I think it's OK to talk when only two players are in the hand.
Also you can check a Daniel Negreanu blog post about that rule.
There is no rule about trash talking in the WSOP. As long as your banter isn't considered threatening to another player you can say pretty much whatever you want. It's poker. The only thing Gold could have potentially gotten in trouble for in the above mentioned video is discussing his hole cards before the hand is over. But I think that rule has only recently been subject to strict enforcement.