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Are you itching to get your hands on some Facebook or Twitter shares?

Be careful. It's starting to feel a lot like 1999 again in the market for hot Internet initial public offerings. And we all remember how that ended.

Still, there are some good opportunities to make money in the big wave of Internet companies going public this year, as long as you watch the prices and buy selectively.

Some with the best potential include Kayak Software, an online travel company, Skype, which is still shaking up the telecom world, and Demand Media, a content company.

And what about the big four -- Facebook, LinkedIn, Groupon and Twitter? Hard to say, because their plans are sketchier and they haven't revealed financials.

What numbers do leak out suggest troubling valuations. Facebook, which despite the buzz seems more likely to go public in 2012, looks pricey if you believe the $50 billion valuation and an estimated $2 billion in sales often cited in the press. Given its rapid growth, that valuation could get more reasonable, though. Marketers will spend $4 billion on Facebook advertising this year, predicts eMarketer. But we'll have to wait for public filings to know anything for sure.

Before we take a closer look at the big upcoming Internet IPOs, let's consider why we are now in Internet Bubble 2.0.

1. IPO valuations are crazy again

I recently spoke with "Investing in IPOs" author and dot-com millionaire Tom Taulli about all the hot Chinese Internet IPOs now hitting the market. The conversation brought a troubling déjà vu -- because the charts and valuations of these companies seemed so much like the risky Internet IPOs folks were buzzing about in 1999.

Image: Michael Brush

Michael Brush

Take the Chinese online TV company Youku.com (YOKU, news) and E-Commerce China Dangdang (DANG, news), a Chinese online retailer. Youku.com rose 161%, and Dangdang jumped 87% their respective first days of trading in December.

Youku.com has a price-to-sales ratio of 75. That's a common measure of valuation; to show you how crazy a 75 ratio is, Yahoo (YHOO, news) trades for just 6.8 times sales. Dangdang goes for a price-to-earnings ratio of 219, compared with 50 for Amazon.com (AMZN, news).

2. Elitism is back

In the late 1990s, bankers took a lot of heat for handing out hot IPO shares to corporate executives and favored clients. This kind of cronyism always seems to get worse when markets overheat. So it wasn't encouraging to see Goldman Sachs Group (GS, news) recently create a special investment vehicle to try to get around U.S. securities law and give its elite investors early access to Facebook well before any IPO.

So it's quite possible investors who aren't those favored clients will face the same conditions they did during the tech boom (and most major IPOs since then, to be honest.) You'll have to buy at inflated prices in the hours and days after shares hit the market, or wait in hopes they dip as time goes by.

Which of course, is not what you're hoping for if you chase a hot IPO.

3. The magazine cover kiss-of-death returns

Back in December 1999, Time magazine marked the top of the Internet bubble by putting Amazon CEO Jeff Bezos on its cover as person of the year. The crash started in March 2000, and it would take 10 years for Amazon stock to recover. Investors cite this as an example of the "magazine cover indicator" -- where popular magazines often mark the top for stocks, with cover stories on bull markets.

Ominously, Time put Facebook founder Mark Zuckerberg on its cover as person of the year last month.

So be warned. "Whenever you have these IPO boomlets and the market gets hot, that's usually a risky time to buy," cautions James Angel, a professor of finance at Georgetown University's McDonough School of Business.

On the bright side, IPO experts like Angel and Lise Buyer of Class V Group, which helps companies navigate the IPO process, say it's positive that so many companies are going public now, given all the concerns that the number of U.S. listings is shrinking. "The IPO market is not broken, it's selective, and that is a good thing," says Buyer. (Read "How the stock market is killing jobs" for more on this.)

Now here's a closer look at some upcoming Internet IPOs to play -- or to avoid.

Kayak Software

Kayak scours the Internet for the best deals for travelers. It collects fees from airlines and hotel chains when travelers book trips. It also makes money from advertising.

Started by the co-founders of Expedia (EXPE, news), Travelocity and Orbitz Worldwide (OWW, news) in 2004, Kayak could have its IPO within the next few months. The recent strength of the shares of online travel companies Priceline.com (PCLN, news) and MakeMyTrip (MMYT, news) suggests there will be a lot of interest, says Nicholas Einhorn, a research analyst at Renaissance Capital, which specializes in IPO investing.