Silicon Valley’s finest want to connect all your devices to the Internet. This will have benefits, but it won’t be risk-free. For instance, hackers could hijack your car — while you are in it.

If this sounds preposterous, it shouldn’t. Wired magazine reported last week how some “friendly” hackers took control of a Jeep Cherokee while a reporter was driving it at highway speed. All they did was bring him to a stop — but they could have done much more.

They could do this because modern cars are essentially computers with wheels. Microchips control everything from fuel injection to windshield wipers. If those chips can talk to the outside world via satellite or cell phone, a clever hacker can make the car do whatever he wants.

This isn’t new, by the way. Experts suspected foul play in numerous “suspicious” crash deaths in recent years. Buzzfeed journalist Michael Hastings died in 2013 when his Mercedes suddenly accelerated straight into a Los Angeles palm tree. Hours earlier, he had told colleagues he was working on a “big story” and warned that the FBI might contact them.

No one could prove hackers killed Hastings, but the latest Wired story got at least one automaker’s attention. Fiat Chrysler issued recalls on 1.4 million cars and trucks because they were vulnerable to hackers. You can bet other companies will do the same. Practically every car made in the last few years has similar systems.

The costs will add up quickly for manufacturers, but they may have only themselves to blame. Wired editors actually showed Fiat Chrysler their proof, but the company didn’t issue the recall until three days after the magazine published its story.

Worse, Wired writer Andy Greenberg says the company knew of the problem nine months earlier.

What does this tell us?

Despite numerous high-profile hacking incidents, business leaders still aren’t taking the risks seriously. That mistake will cost them a lot of money.

For instance, suppose you are a trial lawyer. You just learned that Fiat Chrysler knew nine months ago that its cars could be hacked. How many people died or had serious injuries in Fiat Chrysler cars during those nine months? I’ll bet it is hundreds, maybe thousands. The lawyers will find those people and turn every wreck into a multi-million dollar settlement.

Liabilities will then cascade through the supply chain. Fiat Chrysler will blame its technology providers, who will blame their subcontractors, who will fire people, all because of one hacking vulnerability.

There could be thousands more.

This goes way beyond cars, too.

Imagine the potential for mischief when we all live in “Connected Homes.” If the refrigerator doesn’t poison you, the waterbed might drown you.

You could try fleeing to a desert island… but you’ll need a plane or ship to get there.

Oops.

Hackers won’t stop the Internet of Things, but progress will be slower and more expensive than the techno-dreamers think.

Some high-flying tech stocks will fall back to earth.

Don’t own them when they do.