Mirroring for Performance/Reliabilty:
Mirror FTP and WWW at multiple sites for performance, reliability,
and to provide services when your connection is dial-up.
Legal Implications of Publishing:
Are you responsible for your users' pages (and mail?); a near
miss for ExNet in the UK's first Internet libel case.
Hosting Porn and Pirated Software:
Do not leave read/write areas under FTP (or WWW via more obscure
mechanisms) or you may be held responsible for what gets put there.