There are many different types of currency in ordinary, non-network use: cash, personal checks, cashier's checks, money orders, credit cards, debit cards, bearer bonds, and so forth. Each of these has different characteristics along a number of dimensions: anonymity, security, acceptability, transactions costs, divisibility, hardware independence, off-line operation, etc. Likewise, for a rich variety of commercial transactions to develop on the net, it will be necessary to have a variety of currency types in use.