this is how you tell if you here access to the server that hosts the RSS feed
http://ask-leo.com/is_there_a_way_to_track_unique_subscribers_to_my_rss_feed.html

something like http://www.feedburner.com gives you more info. But as LJ doesn't seem to expose the logs we couldn't tell from that. I'm going to ask the blogsearch folks I know if they get those details for LJ the way they do for individual blog sites. how many people read a feed is one of the values they use to see if a blog goes higher in a list of search results.