The Colorado Bar Association Ethics committee has issued an opinion, not yet formally published, that collaborative family law is per se unethical when the agreement calls for disqualification of the attorneys if the matter must be litigated. Further, a client cannot validly consent in advance to the withdrawal of his/her lawyer in the event the matter goes to court. Here is the opinion. The Kentucky Bar Association's ethics opinion E-425 here, and cited by the Colorado Bar, gave a "qualified" yes to the collaborative law questions presented, while acknowledging that all the ethical issues have yet to be addressed.
Lest you think this is the death knell for collaborative family law, John Crouch has posted at Family Law Newsletter Critique of Colorado Ethics Opinion on Collaborative Law and More info on Colorado Opinion - 4-way contracts? as well as his initial thoughts, Colorado Ethics Opinion against Collaborative Law.
UPDATE: From the Legal Profession Blog an interesting discussion is here.
UPDATE: Pauline Tessler adds her "grain of salt" here.
UPDATE: Check out Diane Levin's excellent post update at Online Guide To Mediation.