I am one poster who has mentoined not logging out of stuff and lending laptop to teenagers.
I am not worried about the (frankly ludicrous) situation that Aitch posited.
the situation is more likely to go:
I am logged in (as I am, generally - it is my personal laptop). THIS DOES NOT MEAN THE WINDOWS ARE PERMANENTLY OPEN
teen borrows laptop, and wants to use FB. sees my page, thinks 'oh right, Frothing's not logged out' - logs me out, and them in. wanders off in vague teenage manner.
teen has no clue who I am on MN - why would they? I doubt they even know I use it.
I wander back, and don't realise teen has use dmy laptop, therefore have no knowledge that they are now logged in on FB (since they ahve no trust issues, and are permanently vague, being teenagers)
I accidentally click the FB like button. (and since there is no two step process, it posts straight away, even if I cancel it, although I don't always get the 'cancel comment' box pop up anyway - have been trialling how and when it posts to my wall)
it posts to teen's wall. who now does know I use FB. and might pop on for a look around. and I am logged into MN on my laptop, as I always am - no need for me to log out generally, as I don't leave windows open for teens to realise that I MN.
teen now has easy access to MN (it having been flagge dup nicely as somethign that might be interesting), and easy access to my posting history.
no braodcasting of wanksock has taken place by me. no flagging up of teen issues has been doen by me.
but regardless, teen is able to read something which I might not want them to - whether it is about the state of mine and dh's relationship ,a health problem, whatever.
not really so difficult to envisage as a scenario, actually.
as I said in an earlier post, the vety leadt MNHQ could do is ensure that these changes work in the way they are supposed to, along with actually flagging up to users that these changes are taking place, rather than just sneaking it thorugh without comment.