Yeah the very idea of constantly having dozens of tabs open at once when you are really only paying attention to a few is yet another enourmous drain on the net as a whole.
FF has done this before by precaching data from links before you clicked on them. Sure it makes clicking on the link faster (IF you click on it) but in the mean time it's DLed 10 times as much data as you wanted or needed.
All those kinds of features (restoring 40 tabs on startup etc) is a drain on your own account (which for limited accounts like sat. or 3/4G can be quite harmful) but it's also a needless drain on the servers, your local loop and even the very backbone itself :/