You mean a "server"?
This "cloud" terminology is merely a metaphor for the general public to explain 'not on your local computer, somewhere on someone else's server'.
But you are correct about Dropbox, they by no means rule the server business... just a relatively well designed consumer-grade, kiddy toy by comparison. But you'll see it championed as the be-all-end-all because they give out a free GB peanuts to all the chimps at the zoo. For example, A3 crushes Dropbox, but you gotta pay for it, a detail not popular with members of the new KKK (Kollectivist Klown Kollective).
iCloud doesn't do everything MobileMe/iTools did. Personally I think for what it does, it does it way better. In addition, unless you're a 6-fingered noob, it's also totally easy to set up and sync for iDevices. I think the most valuable part of Apple's strategy was enabling iCloud to be a primary set-up and sync method for iDevices. If you want to attract new users (which they seem to be pretty good at), helps if you don't have support a ton of legacy platforms and hardware to get your fancy new device happening. That's big shift to try and spearhead, I think you'll see Apple pushing further into the more sophisticated services when they build out more data-center capacity.
Remember to remind whining babies moaning about iCloud, that it takes a local server cluster to make any of their petty feature wishes a reality across all of Apple's sizable user base.