Yesterday on the Orange Line I saw a guy with one of those folding bicycles. That struck me as a particularly good idea for dealing with bringing a bike on the subway. Even if customers aren't allowed to bring their bikes on the T during peak hours, a bicycle is still a large and awkward item to deal with maneuvering into and out of a subway car.
I have no idea how much a folding bike weighs, or how much of a cost penalty there is over a regular bicycle, but it is a smart solution in terms of the logistics of physical handling. And I suppose it's easier to deal with when you arrive at your destination as well, e.g. you could keep it in your office instead of having to lock it outside.