DS_Store files are used by Mac OS X to store folder specific metadata information. They are created in every folder that Mac OS X Finder accesses, even network volumes and external devices. Folder level customizations are stored in the DS_Store file, things like custom icons, icon placement, icon size, window placement, list views, custom background pictures or colors, etc. Similar to the Thumbs.db files on a Windows system, DS_Store files are designed to be unobtrusive, which is why they have a . in front of their name, which makes the file invisible in a UNIX file system. Most Mac users will likely never see a DS_Store file. However, if a Mac folder is copied to another file system, say Windows, those DS_Store files become visible.
Deleting DS_Store files from the Mac folders will cause a lose of that directories folder specifics; like icons, window placement, background pictures, etc,. Deleting DS_Store files causes no harm to Mac’s file system. However, unless you have a very specific reason to delete them, you might seriously consider keep them in place since the Mac OS X Finder uses them. Deleting DS_Store files is really only necessary in some specific Windows+Mac shared networking environments.
You can however, stop the DS_Store files from appearing on network drives by executing the following command in the Terminal:
defaults write com.apple.desktopservices DSDontWriteNetworkStores true