We’re trying to get the word out that folks should NOT use actual usernames when creating RSS feeds from LJ to other services, as it may block those folks from creating new accounts at IJ (and presumably GJ and JF as well). Seems the RSS feed creates a “dummy account” at email@example.com in order to feed out the incoming entries. More info at http://stewardess.livejournal.com/277877.html?view=5724277#t5724277
and in comments further down the entries.
Some of these RSS feeds at IJ now have a number of people who have picked them up. According to the response I got from IJ support, no one can delete the actual RSS feeds but the sysadmin. Anyway, I suggest that if you have tried to create an IJ (or GJ) account and found yourselves blocked, leave a comment here, so there is a list for the support ticket. Or even just to see if there are enough folks to affected to put in a support ticket.
And, just in case, if you're at IJ and have subscribed to a feed for someone who appears on the suport ticket list, you might want to check for a username variant in already place and switch to that instead, just in case the IJ sysadmin will delete some feeds for folks.