Why would anyone use MySQL when they can get a =real= database (PostgreSQL) for the same price (free)?

Easy. They each have strong/better points going for them than the competing options, depending upon the environment and workload(s).

Horses for courses kind of thing.

Probably because they only want a simple array persistence layer, as opposed to a real database.

Better make it a web stack before you get it.

MySQL is missing a few enterprise features, but it does support stored procedures, triggers, and foreign key enforcement now. Sun bought MySQL AB, too, in case you haven't heard. It's probably a good thing that the company who owns it is willing to support it.

From my experience MySQL is a no-brainer to install, PostgreSQL requires all that DB knowledge that MS has taken away from SQLServer users.

Experienced SQLServer managers can move to MySQL and do a bit of work but seem to require complete re-training when confronted with something that looks and behaves like a real DB - though I must confess I've not installed PostgreSQL for a while and it may have the 'configure for someone who just wants to get on with it' option.

Anyhow triggers, procedures and foreign key enforcement are only necessary for people who dont know how to emulate them in frontends/backend scripts etc.

Its nice being an old programmer and watching new innovative technology doing what we did years ago....