If they can do this with a Yacht out in the middle of the ocean from thousands of miles away, I assume in Texas somewhere,, where I believe the "Experiment" was performed, than would it be possible to do it with Jetliners

Listen to the Video very very carefully - it states " NO WARNINGS or Bells went off" to Alert the Captain at the helm of the Yacht.
This was done in a kinda "Stealth" mode.
I can only imagine if this were in the wrong hands by some Malicious Clown or Terroist, and hypothetically , say attempted to steer several Jetliners off Course all at once, with them only having enough Fuel to make their trip to the destination, what would happen !!
Disaster !
Watch this Video about Hacking / Spoofing the GPS : http://www.youtube.com/watch?v=ctw9ECgJ8L0