Twitter, for those of you who just fell off the modem truck yesterday, is the service that enables users to send message blasts to folks signing up to receive them. The messages, which are limited to 140 characters in length, are called “tweets” and are often used to describe what the sender is doing at that very moment.

The Twitter twosome recently faced questions about their company for almost an hour at the Wall Street Journal’s D: All things Digital conference, but when it was over the audience knew no more about Twitter’s monetary possibilities than when the Q&A started.

However, the Twitter people did mention a few ideas for making money.

For example, Williams suggested the company could eventually charge for its service – a concept that so far has been antithetic to the online social-networking universe.

“There will be a moment when you can fill out a form or something and give us money,” Williams said.

Williams and Stone also suggested Twitter might offer a service where a person could pay money to prevent others from using his or her name. For example, Kanye West, who has criticized the company for letting others sign up under his name, could pay Twitter to authenticate anyone claiming to be the rapper / singer / self-proclaimed master of the universe.

But would such a service be legal? What the Twitter co-founders are suggesting would be like a credit card company making you pay them to prevent anyone from fraudulently using your name for a credit account. There’s a word for when one party charges another a fee to prevent something the first party could allow to happen. That word is extortion.

It’s kind of like those old gangster movies where thugs approach storeowners about purchasing a little fire “protection,” remarking how easy it would be for the entire building to go up in flames.

But maybe they were joking. Aside from throwing out a few possible ideas to turn tweets into gold, neither Williams nor Stone actually revealed any concrete plans to turn Twitter into a profitable company.

For instance, that old Web warhorse known as banner advertising didn’t exactly excite the Twitter execs. Although they didn’t rule it out, Williams told the audience he regarded banner ads as “probably the least interesting thing we could do.”

Other than deflecting questions on how Twitter might make money, Stone and Williams did relay some concrete answers at the conference.

For example, Williams did say one of his top priorities was hiring more people to help grow the company. Although he didn’t say how many people he was looking to hire, he did say Twitter currently has 43 employees, which according to Williams, is twice as much as the company employed in January.

The co-founders also admitted to knowing the Twitter hype won’t last forever.

“If you pay attention to it too much, you can run yourself off the rails,” Stone said. “Pretty soon, everybody’s going to hate us.”