Would you go to court with the same Lawyer as your opponent?
NO, Same rule applies here.
Although 100% legal in Mass and NH a Listing agent can represent a Seller and Buyer in the same transaction, but it must be disclosed to both parties in writing. At which point it is agreed by both parties the Agent then has little say / service to both clients in the negotiating process.
CLICK HERE for 10 Reasons why you should use an exclusive Buyer's Agent