While driving in traffic there were loud popping and crackling sounds from the rear speakers. Then smoke appeared and an acrid burning smell. The smoke and loud sounds continued after I pulled over and turned the key off. I removed the fuses for the sound system and it remains inoperable. I went home and searched for this problem on the web and discovered that it is a common problem on 2014 Mercedes E350's. Despite this being cited as a common problem by owners, there is no recall. I called Mercedes-Benz USA and they reported that they were not aware of this problem. This event was very alarming and could have caused an accident when the smoke was coming into the passenger compartment. I believe it qualifies for a recall.