Originally Posted by
BCRider
I'm assuming here that you actually meant to say a side by side quad or trike. An actual two wheel bicycle with side by side seating would only be rideable by circus folks with a hyper keen sense of balance, reflexes and excellent timing to work on the starts. And if it IS a true bicycle being done as a stunt bike then I NEED to see pictures to join in the fun
Sociables are true (two-wheeled) bicycles with the riders sitting side-by-side. They don't require undue skills to balance and can even be ridden solo although they lean over quite noticeably when this is done - to a lesser extent when there is a great disparity in the weights of the two riders.
Usually the cranks are rigidly joined so there is no option for independent coasting (as is also the case on most tandems although there are exceptions).
Here's an article that also includes a few pictures:
http://en.wikipedia.org/wiki/Sociable