So when I take the key out of my ignition the audio system remains on. It started happening last night. I parked at a friend's house and everything was turned off. When I went to leave the radio was playing but the keys to my car were in my hand.

The fuses for the audio system have been pulled so it doesn't drain my already crappy battery. I am replacing the battery tonight since it is only pulling 12 volts instead of the normal 13, according to the guy at Les Schwaubs.

Any suggestions on what the problem could be?

 

Replacing your battery was a waste of money and pulling the fuses was a waste of time.

This is what the BOSE system does. It started happening the second you drove the car off the lot but unless you have the audio cranked when you shut the car off, you don't notice it. As soon as you open and shut the door, it goes off. Something is supplying it with some residual juice but I don't see any reason for concern unless you plan on sitting in your vehicle for 30 minutes or more after you kill the engine.