[vonmoltke]

This probably works great if you have evenly-sized, relatively stable teams. The place I just left has teams that ranged from just me to the entire eight-persob company, and the teams could change on a month-to-month basis. In fact, it wasn't unusual to be working on two or three projects simultaneously.

[cableshaft]

Well, you could have a primary team you work for, and then get called on to work on other things for other teams periodically (while staying at your same desk). That's pretty much what we do here. My team lead is always the same person, but sometimes I do work for the other two team leads, especially when work is light in the current iteration for my normal project.