-There are any number of race conditions that may result from the fact
-that account names are not unique over time. Moreover, it's a bad
-idea to perform lengthy operations while holding the database lock.
-In order to deal with both of these problems, we use a worker thread
-for each account name that ever exists. On 32-bit systems with large
-numbers of accounts, this may cause the NM process to run out of
-*virtual* memory! This problem may be remedied by decreasing the
-maximum stack size.