After you sync a file in Windows Vista or in Windows Server 2008, the Date Modified time for the destination file may be updated to the current time. This behavior may cause a re-sync of the file attributes and may cause the Windows Search service to re-index the whole file.
For example, you click Always Available Offline to pin a network folder in Windows Vista. You visit the folder, and then create a file in the folder. You select Work Offline for the folder, and then replace the file. When you sync the file, the file is synced from the client to the server correctly. However, when you sync the file again, the file is synced from the server to the client again, even though no content changed during this period.