I can't honestly say that if my local police force started podcasting that I'd hurry on over and subscribe.
“They are especially popular with students and we hope they will download our latest topical safety messages along with their favourite tunes and radio programmes."
Maybe I'm alone here, but does that sound likely? When I was a student, I didn't care less about the local police force - that was totally uncool and I can't imagine how much ribbing I would have taken had my cohorts found a police podcast on my massive Sony Walkman.
Sooner or later we're going to get a universal rating system for podcasts a la Technorati for blogs or Google for websites. Once we do, I'm going to be all over it to see what podcasts are actually being useful.