blot means that you are struck out of crossed over from their friend list. But if you are unlucky it means they call the cops on you claiming for example that you have harrassed them. So be careful with unbelievers and false brethren.
(Exodus 32:32 [KJV]) Yet now, if thou wilt forgive their sin—; and if not, blot me, I pray thee, out of thy book which thou hast written.
First occurrence of blot shows that it means to struck someone out of your book, like your friend list, like someone decides he is going to be your worst enemy. Now if he knows a lot about you and your sins then he might be able to do you harm through false accusations or just by the fact that you have talked to him.