Regardless of the thief-deterrent reasons, I think it would be great to have a “last purchaser” record. One of the sadder parts of having a shop stand is not knowing who came to buy your stuff. I think it would help foster friendships and relationships 
I am also strongly supportive of the X-per-patron shop stand idea.
The last thought I have is that people in general should not think of portals as zero-sum. People have as many portals as they find useful. There’s nothing to actually be gained by trolling other portal hubs on the same planet. If I want a portal at X place, having no tokens available there won’t deter me, I’ll just PM the owner… if Y place wants portals they need to provide a useful hub.