If you are talking about the File Sharing control panel and not simply shared files in Limewire:

Limewire is unable to access File Sharing, which is done through Users and Groups and Apple's own protocol. I suppose if you had unrestricted access (i.e., guest with no password) in File Sharing, then a clever but evil Mac person who figured out that you had a Mac and then figured out your IP could access your computer and those files which you had designated as shared (you do that through info., command+i for a folder, drive, or file).