There are lots of ways to protect yourself from unwanted calls (and by protect I mean avoid being annoyed). You can have an expiring Numbr, or you can add repeat offenders to a wrong-number contact list. For everything else, there's Grand Central.
Grand Central lets you set up new phone numbers, totally free, to add to your current phone lines. If your cell phone is a different area code from where you live, your Grand Central number can be in your current area code.
Depending on the person you give your "new" number to, you can set it up to ring on your cell phone, your landline, or both at the same time. When you answer, Grand Central's ListenIN feature screens the call by telling you the name of the person calling, and you can choose whether or not to answer or to send to voicemail.
If you, uh, never want to talk to that person again, you can set it so Grand Central tells them that the number has been disconnected. Met someone out and about and not sure if he's okay? Grand Central lets you decide later if you want to let him in or not, no fake numbering required. Genius!