It's OK to use PostgreSQL as a message queue. Sometimes.

There is currently a great article on the front page of HN related to MySQL and queueing. MySQL does not have the fundamentals for a proper queueing system. PostgreSQL Does.

I outline why here: http://ryandotsmith.heroku.com/2011/09/queue_classic.html

You can see for yourself here: https://github.com/ryandotsmith/queue_classic