Edit: It might be useful to add an optional parameter in some of the link-creating stuff where the programmer can add some sort of "hint" which the base system will use, so instead of http://example.com/a?fn=fkg34lk you get http://example.com/a?fn=voteup_fkg34lk

Or possibly just "make it long" and just have the base system add a number if the id clashes: http://example.com/a?fn=voteup-maybe-something-related-to-3