This is going to be a quick one, for now. I've noticed (as you probably have) that a lot more people seem to be just putting items on their watch list, rather than bidding on them when they're interested, This is no doubt because they don't want to call attention to the fact that they want the item, and to avoid driving up prices.
However, I think some people forget about items on their watch list. I've had some people watching books of mine for 60 days or more. I'm about to take some items down, but it would be nice to have a way to contact these watchers (privately, of course) and offer them a better price before I take the things down.
So I suggest a "Best Offer to Watcher" feature or such. Now it may be there are some problems to this I haven't thought of, but I think if eBay makes the contact watcher link anonymous for the watcher, it would be OK.