Mac OS X has an annoying habit of littering network shares with .DS_Store (Desktop Services Store) files. If you only use Mac OS X and other Unix based systems you may never actually see them, but in mixed environments they can become a bit of a nuisance. There is nothing critical stored in .DS_Store files, just Finder specific settings, such as icons size and location, view settings, etc.
To prevent .DS_Store from being created on network shares, run following command in terminal.
defaults write com.apple.desktopservices DSDontWriteNetworkStores true
To revert changes and resume .DS_Store file creation run:
defaults write com.apple.desktopservices DSDontWriteNetworkStores false
For the changes to take affect you need to restart Finder (or log off and log back on again). This only affects the user account from which the command was executed. Also, it affects network storage (not local or USB drives).
This should work in Mac OS X 10.4 and later.