Paid society definitely has a point, but, like what David said, "Living in society means that you can't realistically have an expectation of total and complete privacy"
Walking into your home without permission is trespassing, but it's not illegal to knock on your door and give you a introduction. You have the right to ignore him, turn him away, or ask him to come into your house for a cup of tea.
With phone calls-they can call you as long as it's within a reasonable time set by the law (8am~9pm), and you can ignore them, turn them away, or accept their offer. You can ask them to take your # off, and report them if you don't.
I noticed that sometimes TMers and door-to-door salesman have really good offers, probably because they'd be out of business without attractive offers. Many of them (esp credit card, debt solutions, etc) are nothing but junks, and instead of just getting frustrated, you should mess with their heads, call them back until they get annoyed, or unleash your anger on them.
Stop whining, and start giving solutions-tell people tricks like barring #s, setting ringtones to silent when unknown caller IDs, etc.