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Almost half of Americans believe Facebook's success will fade as the social networking site is forced to make way for newcomers, according to a new poll released Tuesday as the group prepares for its highly anticipated initial public offering this week.

Forty-six percent of those surveyed in the Associated Press-CNBC poll said they believe Facebook will "fade away," while 43 percent said they think the company will continue to thrive for a long time. Expectations for the social networking site's long-term success was even lower among younger adults, 51 percent of whom said they think the company will fizzle.

Exactly half of Americans indicated in the poll that they believe Facebook is "overvalued," while just a third of those surveyed, 32 percent, said the $100 billion valuation is a fair reflection of the company's worth. Still, 51 percent say buying Facebook strikes them as being a good investment.

The survey also found that 36 percent of Americans have a favorable view of Facebook founder Mark Zuckerberg. Another 30 percent said they didn't have a positive or negative impression of the Harvard dropout, while 14 percent said they have an unfavorable view of him. People who have seen the movie "The Social Network" were also more likely to have a favorable view of the billionaire.

Meanwhile, only 18 percent of those surveyed said they have strong confidence in Zuckerberg's ability to run Facebook once it becomes a publicly traded company, while 40 percent said they are "somewhat confident" that he will perform well.

The majority of Americans, 56 percent, say they currently have a Facebook page, and 3 in 10 people said they use the popular networking site daily.

The Associated Press-CNBC poll was conducted May 3-7 among 1,004 adults and has a margin of error of plus or minus 3.9 percentage points.