One thing about LiveJournal’s feed usage is that they do one fetch per feed every hour or so, regardless of the number of subscribers. New items are just inserted as new journal entries in the pseudo-journal for that feed. Then, those people hammering it just deluge LJ.
I’ve heard that Bloglines doesn’t do the same, which is a bit surprising to me. Pooling feed checks would seem to be one of a slew of benefits possible with a centrallized web-based feed aggregator…