Actually, having a SIM Card in the 1D makes perfect sense.
If they can do wireless shooting with Wi-Fi they can do it over 4G.
Apparently large sports publications at events like the Super Bowl already have a setup for tethering cameras so that they can deliver images back to the office in real time as they're being shot, but Canon could do one better and make that capability standard.
For people running around the Olympics I'm sure it would be very useful, with a venue that large and spread out it would be almost impossible for anyone to set up a private network to cover the whole area, but keeping all cameras connected to the company servers all the time would keep everyone up to date in real time.
You can imagine how useful that would be in places like war zones as well (though probably a security liability at the same time, cameras would have to use encryption and connect to a military channel exclusively. It's an interesting topic).
Amateurs would probably also enjoy having the occasional backups sent straight to cloud servers (on cheaper bodies it would finally be a reasonable way to offset the lack of a second card slot), you could watch a time-lapse project as it happens without actually being there.
AND the camera would have a globally trackable ID, they could probably give it the ability to lock down in the case of being stolen, making the camera worthless to anyone but the owner, and still trackable.
Large corporations could have batches of cameras configured at the factory to make it impossible to remove the SIM card and include a small internal battery to power the data connection.
(Ooh, and Canon could test their own prototype bodies and get real time telemetry during use, it would be like a Formula 1 team watching the race every time a Canon Rep goes out shooting.)