[geoffeg]

DB-level locking is planned for MongoDB 2.2 which should be out within a few months.

https://jira.mongodb.org/browse/SERVER-4328

[spidaman]

Meh, if your other option is to use PostgreSQL and get row level locks, a db level lock is still a fail.

[j-kidd]

And here's a great post that provides some insight on how much effort has been put in by RDBMS vendors to handle locking:

http://stackoverflow.com/a/872808