There are not enough buyers on this site to make Best Offer feasible. Anyhow, it's a tool of the inept seller, i.e., someone who doesn't know what they want for their items or someone who automatically overprices. I don't think eBid should cater to the lowest common denominator. I'd rather keep the current system of having sellers list at the price they want. It keeps the up-front prices more realistic and will attract more buyers over the long haul.
In using Best Offer at FleaBay, I found it to be not very useful. Most buyers don't make offers, and the few who do are not serious about it. I get more sales from genuine auctions and from fixed price listings. A fixed price listing with a Best Offer option isn't really a fixed price listing, is it? I emphasize the word "fixed".