For example, I give my wife access to my tumblr account where I post poetry and my askfm account where I have maybe 10 penpals and 250 followers. Why? Because I do not do anything that I am ashamed of like flirting, sexting, nude photo's or clandestine hookups, etc. In fact, sometimes I even introduce my wife to my online friends and in one case my friend from Barcelona texts my family and has video chats with my wife and my daughter. Why? I have nothing to hide.
Rule #1 - if you have done nothing wrong, you have nothing to fear.
Rule #2 - if you are married or have a partner and are using social networks for flirting, sexting, exchanging nude photos or arranging 1:1 clandestine hookups, you are guilty of cheating and your unethical behavior will eventually destroy your marriage and your family.
Remember, people who cheat, can never be trusted.