The first home I put an offer on (and was under contract for) was with an agent that I found through an open house. When I started to get serious about an offer, he started talking about not needing an inspection, since the home already had one from a previous failed contract. That didn't sit well with me, so I found an independent agent, and made my offer with her. He was NOT happy about losing the double commission. Negotiations were horrible, but we finally came to an agreement. When the inspection came back, we found that NONE of the previous findings were actually fixed, and the inspector found that the carport was in the process of collapsing; all of the support beams had rusted through and falling over an inch. Findings were estimated in excess of $10,000. When we went to negotiate a fix, he said, in law-ese, that since the contract stated inspection findings exceeding $3,000, they would give us that money off the purchase price and no other negotiations would occur. My agent was smarter than that and got me out of the contract with my earnest money (returned 5 WEEKS later). That guy was a jerk.
This was an extreme case, especially since the broker was a friend of the seller, but I came out of it with a hard and fast rule: Never go with the same person on both sides.