SandBox could (or should ?) have a special META tag in header.tpl to prevent indexing URLs by robots such as Google etc. because it's often misused by anonymous URL spammers to get their position high in search engines. When there will be no indexing of the page with SandBox there will be no effect and interest to put links by spammers.
Make a White/Black list feature of domains/URLs (matching regexps ?).