MobileMe was originally demoed with a file sharing feature, allowing a user to upload a file to their iDisk and then choose to share it publicly with or without password protection. Apple even went so far as to allow you to set an expiration date on the link that you gave out to friends.
When MobileMe was launched the feature was mysteriously absent. But on the 12th Apple finally let the feature loose to all of those MobileMe users.
Unfortunately I don’t have MobileMe so I was unable to test the service before writing this post, but if it works as well as it seems I’m sure it will be a great way for those who pay for MobileMe to share files with friends and family.