Via the WSJ (emphasis added)
Nomar may be the most extreme example of a problem plaguing 911 response centers nationwide: false emergency calls made from cellphones that no longer have a contract or prepaid minutes with a wireless carrier and so can avoid being tied to a user. Under federal rules these disabled phones, which can't make ordinary calls, must retain the ability to dial emergency numbers.
Abuse of these phones has become enough of a concern that many 911 officials and some in the telecom industry are urging the Federal Communications Commission to shut off or phase out the emergency feature in the interest of public safety.
In the San Francisco Bay Area alone, anonymous dialers have made tens of thousands of false 911 calls since 2007—with Nomar alone believed responsible for over 30,000. (Call-center operators can detect a disabled phone in part because no phone number shows up on their screen.)
During a 24-hour period on Thanksgiving Day 2012, dispatchers at the city's Department of Emergency Management reported 1,527 false 911 calls—more than one a minute. They believed all the calls came from just five phones, based in part on the cellphone towers from which the calls were connected...
At the root of the problem is a 1997 FCC requirement that all carriers include emergency-dialing capability on cellphones whether they have working service or not. Back then, 911 centers supported the feature as a potential lifeline.
"Cell service was still a new thing," said Trey Forgety, director of government affairs at the National Emergency Number Association, a trade group of 911 centers in Washington. "We wanted people in dire straits to have reliable access to 911."