I think it would be cool to have a feature that would show who mostly sells an item. Would be nice to use as just a reference incase none are up but the person is online.
For example I've been putting up a bunch of ccb pumps and avatar bloods. Since some times I forget to put up my supply. People would just /tell me if they need some instead of waiting for me to put it up.
To keep it from becoming a monopoly, might be good to put up top 3~5 suppliers. Hmm, now that I think about it. Would something like this use a lot of cpu power from sorting all the DB entries?