One factor which you haven't taken into consideration is diversity. Not all the users will be downloading at their maximum rate all the time. With common internet activitites like browsing and email, only a very small proportion of the online time is spent downloading. A ratio of 50:1 has commonly been assumed for consumer use, and 20:1 for professional use. So I would think that 100,000 users could easily be accommodated on a satellite link.
I guess that's my whole point, that an equivalent of 'contention' would also exist for satellites, though I'd debate the conclusion that 100,000 users could easily be accommodated with at 'upto 10mbps', without being seriously deceptive about the 'upto'. I've no idea how they scale the economics, but my gut feeling is it 'upto 10mbps' only be viable if contention were more like many hundreds, or even thousands, to one. That could have a much greater impact than the the 50:1 to which we are accustomed.
From a quick google, it looks like some sat's use data compression to get around bandwidth limitations, and I wonder if they include that in their proposed data rates and contentions? That's all very well for web browsing, but with bandwidth-intensive stuff like video, zips or compressed disc images, the data is already compressed and so there will be no benefit from further compression.
I've also read in places that Sat links carry strict FUP terms with fast-acting throttles which, in their descriptions stop greedy downloaders from using all the bandwidth (ie contending with others). The net result of that is that even if you're a light user, the first time you try to download something like a 4GB DVD disc image, you'll find it takes all weekend rather than the few hours you'd expect.
Sorry for harping on, but we've all seen how deceptive the word 'upto' has become in relation to traditional broadband, I just don't want to see it becoming even more deceptive.
