I would agree with what has already been said--don't mention Greekchat during rush. I remember that during fall rush last year, there was a girl who rushed at USC with me but was not placed in a house. She had told almost all the houses how she had tried to prepare for rush with GC. She had also posted her thread on GC. When informal came around in the spring, she went through to the three hosues which were participating in informal, but apparently word had gotten around about her story being online.
After reading that she had been cut by all sororities by the second day in fall recruitment, the houses assumed she must not be a quality girl. Problem is, she is actually a very sweet girl, just not your average sorority type. Since you never know who may be reading or who may stumble across in the future, I certainly would say not to advertise that you are on GC.
THe second reason is that recruitment on both sides has always seemed to me like trying as hard as possible to make lots of hardwork and effort appear natural, effortless, and carefree. Saying that you have used internet resources to prepare for rush just doesn't fit into the effortless, carefree categories. Because of all the tips you have learned on GC, I am sure our PNM's will be fabulous. But remember--a good magician never reveals his secrets!