Finder (Explorer with Windows-users) writes files named '.DS_Store' to store metadata like comments and icon positioning.

To turn the storage of '.DS_Store' files off for remote storage locations like SMBFS/AFS/NFS- or WebDAV-mounted, execute this in a MacOS X user's account:

defaults write com.apple.desktopservices DSDontWriteNetworkStores true

Afterwards, reboot or log out if and in to your user account.

This only disables storing them for remote locations - not for local file systems!