It's an effect called 'vocal minority'...

Five bad 11 year olds out of the 5000 people on your server is extremely noticeable due to the bullhorn that is the trade channel. Trade chat unfairly allows a couple people to monopolize intellectual bandwidth, mostly because the signal to noise in the channel on most servers is so low to begin with. This of course makes the remaining 4995 'normal folks' on the server essentially invisible because they either don't say anything in trade, or have it turned off.

If you can get even 20 people in a channel to discuss something intellectual, the 'bads' will go elsewhere due to the decreased volume they have.

This is how it works on Wyrmrest Accord most of the time, at least on the red team - our trade chat is typically something like a discussion of the socio-political pressures Garrosh is under or the implications of the battle for Gilneas as seen by the general Forsaken population. Occasionally we'll get an influx of new players who want to do the rectal linking thing, but they tend to get drowned out pretty quick and life resumes as normal.