Here’s something I’d adore in an aggregator: short-lived comment feed aggregation. Many logware packages provide syndication feeds of their comments, many on an entry-by-entry basis. This is great behavior, but one could easily go overboard with subscribing to a ton of per-entry feeds. I mean, after a few days, isn’t the feed going to go stale, but yet still be something that’s pulsed every so often by the aggregator? It doesn’t make sense to keep it.

There are two ways of handling the behavior of the short-lived part:

1. Die after N. Let the user say, “I want to follow comments on this entry via this feed for N days; after that, unsubscribe from that feed.” Seems easily doable.
2. Die N $time after comments stop. Let the user say, “I want to follow comments on this feed for a couple of days after people stop replying to it; after N $time, the thread is clearly dead, so let’s stop polling it.” This way, you follow a comment feed as long as it’s active. You could even have the software do a rate-of-posting in comments to avoid the last-word types. [Not that I'm a last-worder or anything.]

Just thought I’d throw that bit of meat out there.