Here is the answer I was given from Smart USA rep:
Dear smart Enthusiast, The US model of the 2008 smart fortwo can be flat-towed on all four wheels behind another vehicle, such as an RV. We are aware that the current owner's manual states that the smart fortwo cannot be flat-towed. This is referencing the European model's towing capabilities, which have been modified for the USA. We are in the process of correcting this information in all US owners' manuals. smart USA currently does not provide a tow bar accessory at our smart centers. However, any commercial RV retailer should be able to make or adapt an existing tow bar for the smart fortwo. The smart's bumper structure is already designed to accommodate a tow bar. We have a modification procedure to easily accommodate a tow bar to the front structure of the vehicle behind the bumper, and have already provided these instructions to all smart centers. If you have any other questions or concerns, please contact us via email or by phone at 1.800.smartusa. Thank you for your interest in smart USA. You will be hearing from us soon! Jason Dupree Customer Service