Just to add a bit more information I found about call ID spoofing (yes, it's a crime!):

http://en.wikipedia.org/wiki/Caller_ID_spoofing

Legislation in the United States

On April 6, 2006, Congressmen Eliot Engel (D-NY) and Joe Barton (R-TX) introduced H.R. 5126, a bill that would have made caller ID spoofing a crime. Dubbed the "Truth in Caller ID Act of 2007", the bill would have outlawed causing "any caller identification service to transmit misleading or inaccurate caller identification information" via "any telecommunications service or IP-enabled voice service." Law enforcement was exempted from the rule. Three weeks later, an identical bill was introduced in the Senate. [1] On June 6, 2006, the House of Representatives passed the Truth in Caller ID Act, although no Senate action was taken on either the House or Senate bill. At the end of the 109th Congress, the bill expired (all pending legislation not voted into law at the end of the House term, a.k.a. end of a session of Congress, is dead).

On January 5, 2007, Congressman Engel introduced H.R. 251, and Senator Bill Nelson (D-FL) introduced a similar bill (S.704) two months later. On June 27, 2007, the United States Senate Committee on Commerce, Science and Transportation approved and submitted to the Senate calendar S.704, a bill that would have made caller ID spoofing a crime. Dubbed the "Truth in Caller ID Act of 2007", the bill would have outlawed causing "any caller identification service to transmit misleading or inaccurate caller identification information" via "any telecommunications service or IP-enabled voice service." Law enforcement was exempted from the rule. Engel's bill passed in the House of Representatives. Nelson's bill was referred to the same Senate committee that approved S.704.[2][3] The Senate again passed neither version of the legislation.[4]

In the 111th Congress, Congressman Engel and Senator Nelson once again introduced similar versions of the Caller ID legislation, H.R. 1258. The bill was reintroduced in the Senate on January 7, 2009, as S.30, the Truth in Caller ID Act of 2009, and referred to the same committee[5] The Senate and the House both passed their respective versions of the legislation, but on December 15, 2010 the House passed S.30 and sent the legislation to the President for a signature. On December 22, 2010, President Obama signed the bill into law. [6]

Under the bill, which also targets VOIP services, it becomes illegal "to cause any caller identification service to knowingly transmit misleading or inaccurate caller identification information with the intent to defraud, cause harm, or wrongfully obtain anything of value...." Forfeiture penalties or criminal fines of up to $10,000 per violation (not to exceed $1,000,000) could be imposed. [7] The bill maintains an exemption for blocking one's own outgoing caller ID information, and law enforcement isn't affected. [8]