In some instances, requesting a BIN makes good sense. In fact, I'm having trouble understanding why C&V types have a problem with it. I've read several complaining threads about how the bidding on ebay gets carried away and some item sells for way more than it should. On the other hand, I've read posts here about items that were put up for sale that didn't get nearly what the C&V seller thought they should go for. The requests that I've seen from ebayers for a BIN is to avoid paying some crazy price for an item they want, sort of insurance against a runaway auction. Sellers do it for the reverse, they've been offered a chance to get exactly what they want. If they both agree, why not do it?
BTW, I've never asked for a BIN and I've lost items to someone who did request a BIN. Being inherently cheap, I usually use ebay to find a bargain and very few BINs are bargains.