Don't tell me no one has ever tried it.
If I ever got my hands on Expansion 3 I would definitely try plugging it into the port of a full size ADAM.
Seriously, Why would it not work but the more important question is why would you want to.
To try it that's why.
Actually I suspect that if the port wasn't on the side and in front that you could keep connecting till your blue in the face as long as you have power to the units.
Being as it IS on the side I think you could get 3 connected.