Half of Americans think Facebook is a passing fad, according to the results of a new poll.

And, in the run-up to the social network's initial public offering of stock, the Associated Press-CNBC poll also suggests that half of Americans believe the social network's expected asking price is too high.

(This survey is not scientific. Results are based on readers' responses.)

A narrow majority of adults aged 18 to 35 predict Facebook's appeal will fade down the road (51 per cent), fewer think it will stick around as a service (44 per cent).

The public overall is similarly divided on the company's future. Just under half of adults (46 per cent) predict a short timeline for Facebook, while 43 per cent say it has staying power.

The company Mark Zuckerberg created as a Harvard student eight years ago is preparing for what looks to be the biggest Internet IPO ever. Expected later this week, Facebook's Wall Street debut could value the company at $100 billion US, making it worth more than Disney, Ford and Kraft Foods.

That's testament to the impressive numbers Facebook has posted in its relatively brief history. More than 40 per cent of American adults log in to the site — to share news, personal observations, photos and more — at least once a week. In all, some 900 million people around the world are users. Facebook's revenue grew from $777 million in 2009 to $3.7 billion last year. And in the first quarter of 2012 it was more than $1 billion.

Fifty per cent consider value too high

Just a third of those surveyed think the company's expected value is appropriate, while 50 per cent say it is too high. Those who invest in the stock market are more likely to see Facebook as overvalued, with 58 per cent said so. About 3 in 10 investors say the expected value of shares is fair.

But price worries won't necessarily stop would-be investors. Half the people surveyed say they think Facebook is a good bet, while 31 per cent do not. The rest aren't sure. Americans who invest in stocks roughly agree, although investors who are more "active" — those who have changed their holdings in the past month — are more negative. Nearly 40 per cent say Facebook would not be a good investment.

Young people are more aware of Zuckerberg and have more positive views of the CEO, who celebrated his 28th birthday on Monday.

Overall, one in five Americans say they've never heard of him, 30 per cent don't have an opinion and 14 per cent plain don't like him.

Only about a third have a good impression of the CEO, who has alienated some with Facebook's ever-changing approach to user privacy.

But 46 per cent of people under 35 like him. And a scant 4 per cent of those younger adults say they've never heard of him.

The Associated Press-CNBC Poll was conducted May 3-7, 2012 by GfK Roper Public Affairs and Corporate Communications. It involved landline and cellphone interviews with 1,004 adults nationwide and has a margin of sampling error of plus or minus 3.9 percentage points.