Well, I mentioned I saw Astra, and as it's a sat tv satellite, it is in geosynchronous orbit. But then again, I may be mistaken about seeing Astra... perhaps I just misread the name label.

Ok, good to know that the altitude is correct already (didn't realise you guys were so thorough); and indeed, it makes sense that the 100 most visible (man-made, i.e. not the moon) satellites are quite close to the earth. I guess those make a round trip in an hour or even less, and will be the ones most interesting to see in Marble, as they actually move quite visibly.
I clearly recall lying on the beach in the south of France many years ago and seeing a satellite move, and wondering what it was. Won't have that problem now anymore :-)

Anyway, I still think it would be good to have the GPS sats also show up, even if they are not visible, perhaps with a different setting, just to have the overview...