BlockCypher provides Bitcoin wallet services to larger organizations such as exchanges and payment providers. During the recent fracas of "dust" transactions crowding the Bitcoin network, one of their larger clients, Erik Voorhees' ShapeShift.io, suffered a double-spend attack amounting to 2.6 BTC.
The biggest offering of BlockCypher is what they call a "Confidence Factor" which basically means what it sounds like – if the processor is reasonably sure (as in more than 99%) that a double-spend will not be attempted, the transaction is processed with zero confirmations.
Read further at.
https://www.cryptocoinsnews.com/blockcypher-zero-confirmation-bitcoin-transactions-still-viable/
