There’s nothing like being given the same prognosis as Friendster and Myspace three days ahead of your social networking company’s initial public offering, but that seems to be the will of the people today as a new Associated Press-CNBC poll shows that Americans are pretty split when it comes to Facebook’s life expectancy.

In the United States, 56% of people use Facebook and – this isn’t really surprising – a whopping 81% of the 18-to-35-year-old demographic are lurking somewhere on the site with 55% of them visiting the site every day and 33% of them visiting multiple times a day. While the younger adults might be all in like with Facebook, they’re not a very faithful class of users as a slim majority of them – 51% – think that Facebook is merely a passing fad. Fair-weather friends, indeed. They’re not alone in those conflicting feelings, though, because the general public’s opinion is slightly less pessimistic as only 46% don’t think Facebook has any long-term staying power. Alternately, 43% of the overall population think Facebook will likely be sticking around for a while.

One reason people might not be giving full faith and credit to Facebook is because of – surprise, surprise – privacy issues. 3 of 5 Facebook users don’t believe that the company will protect their personal information. In fact, a paltry 13% trust Facebook enough to protect their data while only 12% feel comfortable enough to make purchases through the site. I wish this poll had asked this assured minority why they feel like Facebook will secure their personal info.

The young-ish majority of Facebook users are also the most interested in Facebook’s impending IPO with 59% of the 35-and-unders saying it’s probably a wise investment (even though you kiddos think it’s just a passing fad? Make up your mind, fickle youth!). The percentage of other generations who think Facebook’s a good place to hedge your bets is about split even, with nearly half of Generation X (ages 35-44) agreeing so and 55% of middle-aged people approve of a Facebook investment.

But at least Facebook CEO Mark Zuckerberg is fairly well Liked among his demographic peers: 46% said they like him. No information on why they like him so, but perhaps it’s because he always looks like he’s having such a good time. Seriously, have you ever seen that man not smiling?

On the other end of that question, 14% do not like Uncle Zuckerberg. That hoodie hoopla probably didn’t help those numbers, either.