FriendFeed slightly over enthusiastic
FriendFeed is the hot new thing in social activity aggregation. The basic idea is that it aggregates all of your activity from various online services into one big activity stream. You can find mine here: http://www.friendfeed.com/esjewett.
Doing this type of aggregation means querying the services where content lives on a regular basis for each user. I signed up this blog, so this blog's RSS feed gets pinged on a regular basis. Perhaps too regular a basis.
Those are the stats for a single day. In case anyone didn't notice, I don't post here all that much, so checking ~65 times per day (every 20 minutes or so) might be overdoing it a tad!
Some other feed-catchers do checks at increasing intervals when no new content is found, with a reasonable maximum interval of an hour or so. Such an algorithm, tweaked for FriendFeed's particular case, might save some serious bandwidth. It might also open up bandwidth and processing time to allow it to stay even more ridiculously up to date with frequently updated content.