I regularly have to check my iTunes podcast subscriptions for problems. It’s not necessarily iTunes fault (case in point, Diggnation recently did something to their feed that forced iTunes to download over and over, which I didn’t care about because they can foot the bandwidth bill for their mistake).
From time to time, high volume podcasts such as the Daily Source Code will have their feed download fail. When I saw Accident Hash fail, I was a little perplexed. I clicked the little alert icon.
I had no idea that was a feature. It’s actually a good way to tell whether you should unsubscribe from a podcast. I don’t know what criteria it uses though.