I came across this post today that lists some vague information about how if you create an account on the AOL Lifestream service with a .Mac or MobileMe account the data may share some stream information. The information is vague and it doesn’t explain what type of data may be shared. They do however show screenshots on how to disable the sharing. I don’t have accounts on either service to test or look into this any further. If anyone has more information on this please provide it in the comments.