Rob,
     I think regardless of what rules you sepcify for a cache, some people
will ignore the rules and treat it like a normal cache.  In the vein of a
traveller only cache (permanent cache used to trade/exchange travellers),
there are caches based on a specific theme (snow, christmas, big boys toys,
etc.).  With the themed caches, you can visit and simply not make a trade if
you aren't prepared to follow the theme.  If you set up a traveller-only
cache, you'd need to decide whether someone could have a successful visit if
they simply signed the log book or whether exchanging one traveller for
another is required.
     With a traveller cache, you can, via your computer, know who is and who
isn't following the rules of exchanging one traveller for another.  It would
take some effort, but you could match up traveller movement with the cache
visits.
     I don't think you'd really need to worry about the cache running out of
carrying several travellers for people to use for exchanges.  I think the
geocaching community would watch and maintain it with their regular visits.
I'm sure that if someone arrived and found the cache only contained 1
traveller, he/she may leave their traveller and not take a traveller.
Likewise, if the cache becomes filled with non-traveller trinkets, regular
geocache visitors could remove those to keep the cache tidy.  I believe that
95% of geocachers would follow the rules and assist in their visits of
helping maintain the cache in working order with their visits.
     

>Great minds think alike.  I have almost finished the travelers only
>cache I've been putting together, with one problem I've been working
>on resolving.  How to discourage non-travelers or encourage travelers
>without making the cache be maintained manually?  I think I have a 
>solution, but I would like to hear some other creative solutions 
>from this group...
>
>Rob 
>Team CHUMP