Why I can see some Note Board that users write on other users profile

Hi

When some users in my organization domain add Note Board in her/his my site or write on another users profile,I can see their Note Board, although they don’t write Note Board in my profile(they don’t write Note Board on my profile but I can see their Note Board). Why this happen and why I can see some Note Board that one user write in profile of another user?

Thanks.