I've got two ideas, but I haven't read this post, so some of them might have been posted already.
I think hijaking a store's all store paging system is every phreaker's dream, and would make a great topic for an episode of PLA radio. On the other hand, there's a PLA issue that adresses just that. Also, this isn't really phone related, but maybe something about pirate radio stations. What do you think?