Credit for this idea goes to Erk in this thread.
Create a new chat filter, like the bad language filter only it cannot be disabled. Add to the filter list the urls for known gold-selling websites (along with the standard typographical X p e r m u t a t i o n s 5 6 X). The result is that any attempt at spam comes out something like: "Visit *****.com to buy cheap GW gold!!!" No profit in spamming that message.
To get around such a filter, gold-sellers would have to constantly register new domain names to redirect to their main site, which anet would then have to add to the filter list. However, that's a race a-net would eventually win because adding a url to the filter would be far cheaper than registering a new domain name and hosting a new page.
C

