Is Facebook a flash in the pan? Nearly half of Americans think so, according to a new AP/CNBC poll.

Forty-six percent of those polled say the social networking giant is likely to "fade away as new things come along," while 43 percent predict it will be "successful over the long term."

And with its long-awaited IPO drawing near, half of Americans also say Facebook's asking price is too high.

Just one-third think the company's expected stock market value, which could reach $100 billion — larger than Ford or Kraft Foods, but less than Google or Coca-Cola — is appropriate, while 50 percent say it's probably too high.

But that won't necessarily stop would-be investors from trying to get a piece of the Facebook pie. Half those surveyed consider the company a good bet, while 31 percent do not.

Americans also have mixed views of the company's CEO and co-founder, Mark Zuckerberg.

Only about a third of those polled have a good impression of Zuckerberg, while 14 percent say they don't like him. One in five have never heard of the young mogul, who just celebrated his 28th birthday, while 30 percent have no opinion of him.

On a positive note, of those who have heard of Zuckerberg, two-thirds say they're at least somewhat confident in his ability to run a large public company.

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