AeroFS isn't merely useful for security reasons (inside firewall), but for moving huge files around a LAN. Dropbox does do some LAN syncing on individual accounts, but being able to share big media files during the capture/edit/publishing process would be a great use case. In a lot of those cases, on location, you have Gig-E or better locally, but a 3G/4G hotspot for publishing a final stream (and general Internet use), so something cloud based isn't viable.