Chrizum, you haven't answered my question yet!
That was because you were spamming. But ok, to answer your question, I didn't guesstimate the amount of online accounts like you did with rankings, because you can view the top and bottom ranks of the world. I only guesstimated the amount people that bought the game but didn't go online yet.
Concering Trauma Center, it's obvious that uploading your score isn't as big a part of the game as is the multiplayer in Call of Duty. The target audience of Call of Duty are young male gamers who want to pwn people online (), whereas the target audience of Trauma Centre is everybody (it's a pretty mainstream game, I think).
I haven't played Trauma Centre so I can't really eleborate any more on the subject.