UPDATE: Now available for Mac too.
UPDATE 2: Looks like it has been temporarily pulled.
Every Garmin user will have 150MB of cloud storage to sync your data (waypoints, routes, tracks, etc.) between different computers. This should be fairly seemless (sic), just log in with your MyGarmin account, drag and drop data into your cloud storage device and it will be synced on the cloud so can access it if you run BaseCamp on a different machine.
And if you need more than 150MB, there’s always Dropbox. As far as I know, Garmin Cloud Storage is only available in the Windows version at this time.