For some reason, Persona 4 Arena is no longer available to download in the European PSN store.
A member of the PlayStation Store team, Jawad Ashraf, mentioned the following on the PlayStation Blog:
Persona 4 Arena has been removed from PS Store on request from the publisher. I haven’t been given any information as to why, just that we obliged with the request. Sorry I can’t be more transparent.
Zen United is the publisher in question, but no information has been given yet as to why the Persona 4 Arena has been removed. Hopefully Zen United will send out an official announcement soon.