Judging by LJ support requests, Google blogsearch is going to be a huge headache here...
1: Even if you have robots blocked, your RSS feed will cause Google to index your LJ. This includes friends-only and private posts!![Edit: No it doesn't, see below or http://www.livejournal.com/support/faqbrowse.bml?faqid=149 --V]
2: RSS includes the first paragraph of all locked posts (although non-friends will still be blocked when they click on the link). [Edit: This is not in fact true as it turns out. Locked posts will only be visible on the feed if the reader is already authenticated with LJ and has permission to view those posts. Phew. I guess you can still run the console command given below if you'd prefer only the titles to show up in your entries anyway. --V]
To fix this:
First, although you cannot completely disable your RSS feed, it is possible to restrict it to just displaying the subject lines of your entries. You can do this by going to the Admin Console (http://www.livejournal.com/admin/console) and entering the following command:
set synlevel title