Keller Williams appears to be the first major brokerage to come out strongly again the AgentMatch Beta being conducted by Realtor.com. They have even taken the step to advise their agents to oppose the rating system.
You can read the entire article from Inman News here.
It certainly looks like a grassroots effort is beginning, to influence individual MLS's across the country not to participate.
Personally, I think this is a fantastic development, and I hope to see other major brokerages follow suit.