I can get a full sized bike with wheels and fenders in the back of my Honda Accord IF I put the seats down, but there isn't room for anything else. I have to haul stuff for work so a folder or external rack are my only choices.
These guys that are tossing 700c wheeled bikes in the trunk with the wheels off don't have fenders and racks and don't have things already in their trunks...Get the folder... trust me.
Aaron