Most of us have known for a long time that caller ID has pretty much become worthless and unreliable as a means of identifying and authenticating a caller. There was a lot of press last year about how caller ID was maniplated as an easy means to access individuals voice mails. Free Voice over IP (VoIP) PBXs such as Asterisk, services such as Spoofcard, applications on your smart phone, etc. make it very each to change caller ID.
One bit of news that hit home with me, was when I saw a warning in Consumer Reports about how easy it is to spoof caller ID. When we start to see warnings in non-technical consumer publications like this, we know we have a big problem :) I provided the page that has the warning. The blurb is in the lower right:
Finally, for more information on the issue of caller ID spoofing (and solutions), check out the TrustID blog.