An article in the Phila Inqr describes how spoofing works, efforts by the FCC to stop it, and what 'spoofing' will still be allowed.
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For myself, as someone with multiple lines, I wish the Caller-ID sent out my main incoming number instead of the exact outgoing line I happen to be using. I notice organizations served by large PBX's (not centrex) do exactly the same thing. People attempt to call me back using the "callback button" feature on their caller-id screen and can't get through.