Make it possible to have aliases (aliases on Mac, shortcuts on Windows) to those items I want to share.

It is MUCH better to have a folder that I share in which I drag aliases to the actual files, rather than directly sharing the folder where the originals are.
Reason is: If I share a folder with all my programs for instance, I may not want to share all those programs, or many of them are already free to download directly from the manufacturers site. I certainly don't want to make copies of those programs I want to share and put them in a LimeWire share-folder. An alias to the items I share would solve it all. Same advantage when sharing music of course.