Sharing of what kind of files schizo?
Anything, you can hardly restrict certain filetypes being uploaded to a server you own. Of course you can set a rule that anyone sharing illegal content would be banned by an administrator, but it's no different to skype.
TBH though, I kind of renege on this idea. Skype is popular, if shit fucks up domestically then you can always get someone to help out, server-side issues won't disable the functioning of the protocol unlike the solution I'm proposing, which requires a working understanding of the Linux command line.