Stalking

When does a concerned interest in someone’s activities become stalking?
I think it is alright to be interested in someone and wanting to know him if it is about getting information directly or through friends and family but breaking into a mailbox or computer is crossing the line of privacy. Stalking begins when someone observes or interferes in other person’s life without his knowledge and permission. People have the right to feel comfortable in their own houses and safe about their private life.

Are some kinds of observance allowable and appropriate? Which ones aren’t?
The only kinds of observance I find appropriate are police surveillance when there is a suspicion of crime or monitoring in public places where something valuable is kept. Using telescope to watch the neighbors is not ok. No matter how pretty the neighbor is, she has the right to keep her beauty private. I would go mad if someone was sticking nose to my private life and the "big brother" would have to face the consequences.