In the recent Ecommerce Benchmark 2006 by Marketing Sherpa, one of the charts shows how 51% of merchants don't allow their affiliates to use the merchant's branded terms and Trademarks in search engine marketing (PPC). This is up from 39% as surveyed in August 2005.

Coincidentally, myreferer.com told me this morning that they don't want me bidding on "myreferer" keyword so I had to stop. I'm not convinced this is a good policy for all merchants to follow. For example super affiliates might be bringing you a lot of business via PPC - much more than you can get yourself. Or you might be getting business indirectly via PPC and cutting off the PPC could cut off the indirect sales.