Likelihood: More likely than you think. This has already happened several times on a smaller scale. In December 2008, Ukranian-based attackers used a phishing attack to gain log-on credentials for Checkfree , an online bill payment system used by more than 70 percent of U.S. banks. In April 2009, an SQL injection exploit at registrar Domainz.net allowed Turkish attackers to take over the New Zealand sites for Microsoft, Sony, Coca-Cola, HSBC, and Xerox, among others. The same hackers also took over all of Puerto Rico's domains. This past January the domain for Baidu, the largest Chinese search site, was taken over by a group calling itself the "Iranian Cyber Army."  In that case, Baidu filed suit against its U.S. registrar, Register.com, claiming it was slow to respond to the site's plea for help.
How to avoid this fate: "Eternal vigilance?" asks Rasmussen. "You want to monitor the hell out of what you and other people are doing with your domains and theirs, so you can turn off the system and anything that connects to it if you or someone you trust has a problem."
Some registrars are hardening their defenses against hijacking and making it tougher to change DNS records, but mostly it's up to domain owners themselves to police their own records and respond quickly when they've been compromised.
Tech doomsday scenario No. 5: God strikes back
News flash: This report is being brought to you via word of mouth, because nothing else is working. Scientists believe an enormous solar flare has struck the earth's atmosphere, causing a worldwide failure of the electrical power grid and communications systems. We are also receiving scattered reports of earthquakes, typhoons, and swarms of locusts, though they cannot be verified at this time.
Think of it as the mother of all power surges. The sun spits out an enormous cloud of superheated plasma several times larger than the earth, which slams into our atmosphere. Supercharged particles travel through the earth's crust, frying all the power transformers it touches -- instant worldwide blackout.
Sound like a cheesy Hollywood plot ? This precise thing happened on a smaller scale in Quebec in 1989, when a solar storm caused 6 million people to lose power .
"The chances of the Internet totally crashing are slim to none, but if anything could cause the Net to go down it would be a solar flare," says security consultant Robert Siciliano. "A plasma ball hitting the earth's magnetic fields that it can't deal with. The step-up and step-down transformers that manage our power grid would fry. It would literally be the perfect storm of cataclysmic power surges that knock out the power grid and the Internet at the same time."
Also: We predict this will occur just as the Chicago Cubs are about to win the World Series.
What could happen: Everything that would happen in the previous four scenarios, and then some. Forget clean water. Forget health care. Wipe out the last 20 years of recorded history, because most of it was stored digitally.