@robbie21 - I think I remember the episode you're talking about. Science fiction always seems to use the idea of a Dyson shell as a rigid, solid structure, which is really a misinterpretation of the idea. (I think I read a short story once where people realized they were living on the outside of a Dyson sphere. They said it was impossible that they could ever have lived on the inside, because inside, gravity would be so high that chickens wouldn't even be able to fly!)
The Wikipedia article on Dyson spheres has some good pictures of what the arrangement might actually look like. You raise a good question, though, whether it would even be right. It brings to mind extreme engineering projects on Earth today (like dams), which so often seem to have unintended consequences.