Bid for Coin is a reverse auction bidding site that auctions bitcoins to benefit bitcoin-friendly causes and non-profits.
The service is located at https://www.bidforcoin.com.
Participants bid small amounts of bitcoin to win larger amounts of bitcoin. The site is distinguished from many Bitcoin gaming sites in that there is no randomizing element. The contests are played by humans against other human opponents in a purely strategic reverse auction game.
Bid for Coin's style of reverse auction is called a lowest unique bid auction, where bids start at 0.001 BTC and increase in increments of 0.0002 BTC. Participants purchase these bids in secret, and the lowest bid that was purchased by exactly one player wins.
After the total of all purchased bids exceeds the prize amount, the prize is awarded to the lowest unique bidder, and the remainder is split evenly between the site operator and a specified cause or non-profit.
Currently, these beneficiaries include the Bitcoin Foundation, the Free Software Foundation, and the Internet Archive.
Any Bitcoin-accepting non-profit can create auctions with a valid Bitcoin payment address.