Sentence:  The difference between responses to the statement, "If someone <WSD>friends</WSD> me, I will <WSD>friend</WSD> them," and "If I <WSD>friend</WSD> someone, I expect them to <WSD>friend</WSD> me back," is telling. 
Meaning of the word marked with <WSD> tags:  To add (a person) to a list of friends on a social networking site; to officially designate (someone) as a friend.