Suggested checkboxes/fields for advanced search criteria:
games within X miles games on my wishlist games for sale games for trade
With these fields you could, for example, browse all games for sale within 60 miles, or narrow the search further.
This would actually generate income for BGG. I have only purchased one game from the marketplace, and that was bc the title was OOP. The price for used copies of the games I've been interested in, after shipping is added, has never been cheaper by more than a couple of dollars than a new copy bought online.
Yesterday I bought a new copy of Aton for $30 ($25+$5). The cheapest marketplace copy with an English rulebook was $28 ($20+$8), and some of the used copies cost even more than the new one did after shipping. The suggested features wouldn't have put a copy of Aton in my hand, but if I could have browsed locally I very likely would have bought something else and taken a little drive with my wife to pick it up before dinner.
And if a game on my wishlist was available (at 33% off, as in the example above) I would always favor the used copy for local pickup over the new one.
EDIT: This thread should really be moved to suggestions. I've posted a link to it from there.