As much as I like reading Slate, I've just unsubscribed from their feed because they can't seem to figure out that it isn't supposed to represent previous articles as new or updated each and every time my aggregator pulls it down. I'm not sure what they're changing on their end every 15 minutes, but it's not the content. Whatever the cause (and reason behind it), it's completely ridiculous that an organization that large can't figure it out (or chooses not to fix it).
Perhaps there is some sort of disconnect between Bloglines and Slate (I highly doubt that because this problem has persisted for a while now), but either way, it's broken for me and they've just lost a reader. :\