Of course, if Apple's iDisk didn't actually suck — didn't actually sync at dial-up data rates, didn't actually take days to sync a few megabytes of files, didn't actually stop syncing altogether at the first file conflict it encountered (which should be conflicting at all), didn't actually corrupt files due to all of the above — then Dropbox would probably have a much smaller market, at least among Mac users.
But iDisk does suck.
And Dropbox is easy peasy.
And Dropbox is also cross-platform, so you can sync across all kinds of computers.
And Dropbox makes individualized sharing of folders possible.
So now I am using Dropbox, and when my MobileMe account expires, I'll have to see if syncing other stuff via MobileMe is worth $99/year. After all, I'm already syncing email and calendars via Google.
This whole situation boggles my mind, though. It's not as if Apple didn't have the resources to make iDisk totally rock.