BuddyPress.org

I’m sure many of user and owner of a site using buddypress, ask himself”do I want my site activity to be indexed by search engine?”. Well I think it would be better for my user to not index the activity,but I have to say that google index most of my activity streams from my site(big exposure) but no privacy for users at all.I would like to know what the buddypress community think about this because it is very interesting to see that there is no privacy for buddypress member(profile show e-mail address,activity show to non member and etc for example).
To come to my real question I have a hard time to figure how to set my robots.txt file to block activity stream and profile page from been index(/directory path).
After hours on my webmaster tool(obviously without success) I decide to ask you guys the solution.
Thank you