I've been told this is due to the requirements of RFC 2617, which defines the way that a client is supposed to be able to log in to a web service. But I find it hard to believe that it's impossible for an RSS client to notice that all of the feeds are all coming from 'www.livejournal.com' (or 'users.livejournal.com') and therefore can use the same authentication. I also find it hard to believe that nobody else has tried to use an RSS reader to read a moderate-to-large number of authenticated LJ feeds, and grumbled about having to enter the same login information so many times.
So, my question - where does the problem lie? Is LiveJournal at fault for requesting different realm information for each different user feed? Or is it the RSS reader's responsibility to recognize that all the feeds are coming from the same place and therefore should use the same login?
(I know there's a kludgy workaround involving using an S1 style to read a friendslist, but that's not what I'm after.)