Mac OS X: Maximum Number of File Sharing Connections
Mac OS X, like previous versions of Mac OS, has a Personal File Sharing limit of 10 simultaneously connected users. This service is referred to simply as File Sharing in some versions of Mac OS X.
In Mac OS X version 10.0 or later, Personal File Sharing is designed to serve a maximum of 10 users. If you need to connect more users at once, you should upgrade to Unlimited-Client version of Mac OS X Server (http://www.apple.com/server/).