M zuckerberg
Mark Zuckerberg,(R) chief executive officer and founder of Facebook Inc. waits in a parked car on July 12, 2012, in Sun Valley, Idaho. Facebook's falling stock price has knocked Zuckerberg off the top 10 tech billionaires list. But he's still worth a lot. - 

Jeff Horwich: Well, easy come, easy go: Facebook CEO Mark Zuckerberg has dropped off Bloomberg's top ten list of the richest tech billionaires. The reason is that shares of Facebook are near record low.

From our Wealth and Poverty desk, Shereen Marisol Meraji has more.

Shereen Marisol Meraji: Man, we are obsessed with billionaires, aren't we?

Kerry Dolan: It's a way of keeping score, people love to keep score.

Kerry Dolan is a senior editor at Forbes, she covers billionaires for the magazine.

Dolan: It's one of the most popular things that we do.

But can you keep score if one billionaire's money is tied up in his company's publicly traded shares and another has hard assets - cash in the bank, gold in a vault, that sort of thing?

Richard Florida: One of the real risks is that you have billions wrapped up in a single company and if that company doesn't perform or succeed, you have an very undiversified portfolio.

Richard Florida's a business professor at the University of Toronto.

Florida: We've created this paper billionaire phenomenon and they come and they go.

Dolan: I don't know, I don't really like the term paper billionaire.

Kerry Dolan of Forbes says there is real value in the company shares that billionaires like Mark Zuckerberg own and that should count toward their net-worth. And, Zuckerberg, he may not be on the ten richest tech billionaires list anymore, but as of today, he's still the B word.

I'm Shereen Marisol Meraji for Marketplace.

Follow Shereen Marisol Meraji at @RadioMirage