Not just "some" people -- ALL of them.
I do believe this from a long experience of mine.
Everyone is a lesson, it's up to you to be aware of your lesson.
Absolutely. I think just about everyone I meet has something they can teach me either directly or indirectly.
Absolutely almost everyone teaches us a lesson or two or three and even if we dont know the reason and we may never will know the reason for some i think ultimately its all for a reason (sorry if that doesnt make to much sense)