Pfizer, the pharmaceuticals megacorp, is jumping on the latest Web bandwagon with a "partnership" with Sermo, a social network for doctors. Lovely. From what we recall of our last physical, doctors are really into poking, but I'm not sure they want to be "friends" with drug sales reps. What Sermo isn't saying: This shows that their earlier business model of selling market research based on doctors' conversations isn't working out that well. Dr. Daniel Palestrant, Sermo's founder and CEO, came up with that business model in order to avoid having to take advertising. "In my mind, I saw advertising and credibility as mutually exclusive to doctors," he said. Still true, despite the arrival of Pfizer's ad budget. A suggestion, Daniel: Limit Pfizer's use of Sermo to invitations to those popular free dinners its sales reps like to throw.