Apple is shutting down the iDisk service on June 30th 2012. This is part of Apple's transition from MobileMe to iCloud.
Existing accounts in CameraSync will continue to work until that date, but you will be unable to add a new iDisk account or re-enter your login details should you remove the app.
You should backup any files on your iDisk (Apple has provided this guide to help you). We highly recommend switching to a different service in CameraSync as soon as possible to avoid any issues.
If you're looking for a replacement to iDisk then we would recommend Dropbox - a very popular service that can sync files and folders between Macs & PCs and also has a great iOS app. If you sign up for Dropbox then why not use this referral link then we'll both get 250MB of extra space.