Hi,
Most people use MySQL because thats what everybody else around them
uses. They lack the expertise, since they are usually "just" developers.
So picking the most popular makes the most sense to them. If its popular
it can't be bad and at least there are plenty of examples, applications
and people to ask.
I do not see PostgreSQL breaking this cycle. So to me the focus must be
on making sure that people that do have the expertise have little reason
to choose MySQL. So make sure that MySQL has no upper hand on features
(like in charset support).
regards,
Lukas
PS: I am not saying that all marketing is futile of course. I would
focus on Universities. I remember that at least at the TU Berlin I saw
much more MySQL than PostgreSQL.