If I deleted you as my friend,

either

1. your posts were negative
2. you weren't really my friend

or

1. You are my friend but I deleted you because I was mad at you
2. You are my friend in the real world
3. You are my friend but I can't look at the shit you post- it makes me psycho/stalkerish
4. I deleted someone that I was mad at and you were their friend; therefore, I deleted you.

and for the special case of 3 people I can think of that I do really love:
1. I acted irrationally to hurt your feelings. sorry.