Here in southern AZ we do 3 or 4 rides a year that we treat as 'races.'

The biggest one that we participate in is El Tour de Tucson, which has something like 8,000 riders in 4 distances.

The organizers call these events 'Rides.' Just try to tell that to the guys who do the 106 miles in just over 4:03!

These events are big enough to attract a number of tandem teams at each distance and the organizers are nice enough to break out the tandem times in a separate list of finishers.

I realize that this is not the kind of racing you were asking about, but its what passes for racing for us.

Your idea of doing triathlons as a tandem team is an interesting one. From what I've seen of triathlons, (I don't do them myself) timing begins when a competitor enters the water. In a pool situation, not every competitor can get on the pool at the same time so starts are staggered. How to get teams together after the swim would be tricky and having the swim after the riding could cause chaos in the pool afterwards... But I like the thought of it.