SNS is very useful to communicate with friends. But, sometimes it is very troublesome. A reason is that it is easy to expand on the community network. I cannot memorize names and faces over 100. Sorry! I then removed some people from my LinkedIn network. This does not mean any offensive attitude to them. My memory cannot follow too many people. Everybody has a range of memory that decides a scope of community for him or her. My scope is under 100. Hope they accept my excuse.