Kevin Spacey tries to explain Twitter to David Letterman. No luck.

Kevin Spacey tried to explain Twitter to a technologically clueless David Letterman last night.

Without much success.

"Does it cost you money to be on Twitter?" Letterman asks.

"A penny for every letter. So expensive, Dave," Spacey jokes.

"Right now, I have over 800,000 people following me," Spacey goes on. "What would you like to say to 800,000 people because you will never get that many people watching tonight?"

Letterman is horrified that Spacey has to type his Tweets with his thumb and not very impressed about hearing "Hello" from so many people.

"I can go out here on 53rd and Broadway and get people to say hi to me," Letterman brags.

Is Letterman turning into the new Andy Rooney?
Does anyone else really understand Twitter?