An entrepreneur yesterday had lots of questions about using Facebook as a marketing tool to help grow his business. He said he looked at Facebook as the new Yellow Pages for small businesses. His clients, he said, are all Facebook users.

He wasn’t nearly as excited, however, about Twitter. When I told him — an educated guess — that many of his clients and prospective clients probably use Twitter, he said he’s “not there yet.” He said he doesn’t see it as a marketing/sales tool.

I tried to explain to him that Twitter is not all about people tweeting about what they had for breakfast. (True story: The only time I’ve ever read anything like that was on Facebook, where a friend wrote “I’m eating a delicious sandwich” as her status update. Still give her grief over that.)

Twitter users are far more receptive than Facebook users to marketing/product conversations. By that, I mean ongoing conversation about a product or service, not blatant, in-your-face pitches. Twitter has the highest percentage of users among the social media sites who are entrepreneurs, according to several surveys.

So what’s the problem? Then I remembered last week’s latest Harris Poll conducted for LinkedIn — 69% of U.S. consumers said they don’t know enough about Twitter to use it. Marketers were particularly harsh in their response to Twitter — 21% thought it wouldn’t go mainstream while 17% said it was “already over.” And only 8% of marketers felt Twitter was an effective promotional tool.

Why the reluctance on Twitter? Why haven’t the Time magazine cover stories and relentless, positive daily coverage (even The New York Times) quieted the reservations of people like this entrepreneur?

When I look at the 69% figure, I think of more than just people needing more information before they use Twitter. Many people still don’t get what Twitter is; it lacks any real identity or clear purpose. LinkedIn is business networking, period. Facebook is social between friends, acquaintances and, increasingly, family. Marketers are just trying to ride the wave of Facebook’s immense popularity.

But Twitter? Many people don’t understand the point of 140-character posts read by strangers. They’re not sure if Twitter is social, business, bulletin board, news, opinion or what. It’s perceived as untamed and unfocused. While Twitter users have the ability to control who they follow or those who follow them, there is still a Wild West quality to the site. Marketers, spammers, porn star wannabes and weirdos can find you easily, even if you can quickly block them. Because Facebook and LinkedIn are perceived as far more protective of the user, people feel safer there.

Brand identity and a quality user experience are the two biggest challenges for Twitter moving forward, particularly as it looks to cash in on its vast audience. And social media marketers and strategists will be challenged in convincing many professionals and small businesses that Twitter is worth a look. Trust me, Twitter is worth checking out.