In addition to weight limits in general I would consider that my tandem forks take more serious hits than my single forks. On a single it much easier to protect the front wheel and fork and my speed on a tandem is at times much higher. I know I have plowed through some holes and bumps on the tandem that I would have easily lifted my single front wheel over or bunny hopped. Heck I once drove our tandem straight over a curb at a 90 degree angle to avoid a car. I automatically tried to pull up on the bars to help the front wheel over the curb. Needless to say that was wasted effort and the front end remained firmly on the ground as we smacked into and over the curb. Both wheels tires and fork survived.
Of course this is dependent on your personal riding conditions and so may not be as much of an issue for other riders.