> By the way, the bank transfer example doesn't really require 
> a transaction. Just withdraw 50 from A, wait for an 
> acknowledgement, and then deposit the 50 in B. And the system 
> might profit from a few milliseconds of float ;-)

Except when you want to handle two withdrawals from the same account
happening concurrently.  You either need a transaction, or you need to
fake concurrency (using a critical section for example).

- Stephen