Relatively simple idea.
Instead of only having the numeric textbox to enter a price, would it be possible to use a set of Radio Buttons to offer a few other options? Namely:
WANTED
=========
[O] Price: [________________]
[ ] /tell
[ ] Trade: [________________]
Just a thought. Could also add filter settings in user profile for people who don't want to see /tell or trade options (or some other combo).
EDIT: Tacking on one more idea. For items which have an AH history, would it be possible to add +/- % tolerable limits for bazaar? If /tell or trade options were implemented, there would be no reason for 1G bids for (average) 300,000G items. A filter for [ANY]+% and [50]-% for example would show any bazaars from 150,000G upwards.
Combined with my first idea (both the options and the filters), I think this could potentially dramatically increase Bazaar usage. (maybe that's just me though?)