Can Backup Directories in ~/Library/Application Support/MobileSync/Backup be removed I have configured my iPhone to backup on iCloud. When browsing the above mentioned directory on my MacBook I find some old files and directories from months ago which are using up 1.5GB of space.

Can these be safely deleted without incurring in problems?
Yes, these can be removed without issue. The usual way to remove backups is through the backups list in iTunes Preferences, which shows the name of the device and the backup date, but there's no problem with removing the folders manually in Finder too.