BPM follows a score-based method.
Older shares (from beginning of the round) have a lower weight than newer shares, which serves to demotivate a cheater from switching between pools inside a round.
Server cheating, by way of the pool operator fraudulently granting himself extra 'shares', is not addressed. Thus the clients have to trust the pool operator to fairly distribute the proceeds.
Balances accumulate on the server, and are sent out when a user-set threshold balance is reached.
There is a fixed fee of 2%, as of March 10, 2011.
BPM was announced on November, 27, 2010. At the time the service was operated under the name Bitcoin Pooled Mining Server and operated on a share strategy that involved an artificially low difficulty method that has since been determined to be vulnerable to cheating.