In life we do things that we think are right. We all do our best. Sometimes though we don't realize what we are actually doing, and would not do those things if we realized what it actually means to others.
I have heard a few friends say that they will basically accept anybody as a facebook friend. They do this because they take the stance that if they turn out not to be someone they wish to maintain the friendship with, they can just block them.
I understand deleting someone, because there are times when you just don't click with someone and as time goes on..you lose touch, and never really had much in common or much to say to each other. You might delete these people, and most of the time, they wouldn't even realize you had done it, or at least, not for quite a while. As in real life, friends come and go, and as people fade away, you lose touch. In facebook terms they are deleted from your life.
Blocking on the other hand is much more overt and direct...and personal. Blocking someone is basically saying to that person " I don't like you, I want you out of my life..I want to make sure you go away and never come back. Don't have any more contact with me...you scare me on some level..disgust me on another level...or just plain I hate you and don't want you around me anymore."
Many who get blocked take that very personally. As they should.
At times, I think it would be more prudent to take the time to see who you are friending and what they are about.
So next time...think twice about who you block and what it may mean to them.
It might not mean much to you, but it hurts them. You took the time to try and be friends with them. Take the time to end the friendship on better terms.