USB ports, Firewire ports and etc… could fail over time, due to physical damage (changing shape) or due to logic-board problem.
The ports are supported with fuses and are powered by some critical chips and main chipsets on your logic-board. If more than one port is not working, there is a chance that your macbook has a major issue. If one port is not working and the shape and physical appearance of the port is okay, then again it could be a logic-board issue. Over all you may need to consider taking your macbook to a shop that offers FREE DIAGNOSTICS. Check out some of the stores that offer Logic-Board Repair and Replacement in Toronto.