Am I Required to Use the Runway Advised by a Unicom?
You are not required, but it is advisable if there are other aircraft in the pattern.  My home airport often does not have anyone in the pattern and pilots that are based there will sometimes land opposite of the advised runway because their hangars are located at the other end of the runway from the FBO.  This means that they can either land long or do a long rollout after landing and then turn off at their hangars.  If they landed on the advised runway, they would having to taxi all the way back down from the FBO end of the airport or applying brakes to try to make one of the turnoffs to the taxiway.  You just listen on the CTAF and announce your intentions if you don't hear anyone.  It is probably more used when a pilot is flying back and wants to just make a long straight in approach while also ending up at his hangar with minimal wait time.