I never realized it until now, but there is no specific forum category for migration from PostgreSQL to MySQL at http://forums.mysql.com/ (only one for Other Migration).
Unfortunately, there might still be more people who migrate from MySQL to PostgreSQL than the other way around, but it should be one of MySQL's big goals to change that - and I believe that this is a realistic goal. The lack of a specific forum category has the potential to make people believe that this is meant to be too unrealistic - so I think, there should be one.
I also recently filed a feature request for MySQL MigrationToolkit to add functionality for migration from PostgreSQL to MySQL (http://bugs.mysql.com/bug.php?id=16508). I know that it's no easy task to provide good migration functionality - but there's probably not much time to waste.
Another idea for a forum category may be to ask people what they miss about MySQL and why people migrate away from MySQL or choose another database system to migrate to than MySQL. Of course, not that many people who don't choose MySQL will come their to report about their reasons, but maybe some people will do - and their opinions could be very valuable for MySQL to find out, what the most important things are that are necessary to attract those potential users and customers.