Very good post for the one who don`t know about this !
About friendly`s it`s a different story , you should not add everybody you see on auction / league / champion or cup and pray to accept the friend request or on the other side received friend request may be a dumb as well that will arrange you unwanted friendly !

Morale : Don`t add random friends and after raping you with an unwanted friendly go on forum > new thread > WHY / F*** / UNWANTED F..