Thanks for the link, gives a great answer to their justification.

Other products (mozy, carbonite, sugarsync) handle arbitrary directories this by: You simply specify which director(ies) and where to sync those on each machine. You can also access all the data via a browser or on-demand downloads. A syncd directory only exists on a new machine when you specifically enable it. There's no automatic file overwriting or replacement issues. Sync is handled the same way as the 'dropbox' folder handles it.

Also, they all have the equivalent of the 'dropbox' folder which is the only thing installed by default -- exactly like dropbox.