NEW YORK ( TheStreet) -- There's been a hint of IPO mania happening during the past year, and while it's nice to see new companies coming to the market, there have not been many names that have captured the interest of this value investor.What has been interesting is the proliferation of companies coming to market that offer free services and generate revenue through advertising. These businesses often ask consumers to pay up for a premium version of their services. I use many of these services personally -- the free versions, that is. I won't pay up for bells and whistles. It's a classic case of "use the products, but don't buy the stock." Some of these initial public offerings have come amid much fanfare, with the granddaddy of them all happening Friday, when Facebook ( FB) begins trading. Let's first look at the stocks of other recent IPOs. 10 Stocks to 'Like' When Facebook Goes Public >> LinkedIn ( LNKD), which operates a useful online professional network, went public at $45 a share last May. One year later, the shares have risen 250%, and many would call this IPO a great success. The company is profitable, but trades at more than 750 times trailing earnings and 18.5 times revenue. Using 2013 analyst estimates, the company trades for 89 times what it's expected to earn, and 8.5 times its forecast revenue. That's far from cheap. While it's a far cry from the tech-bubble IPOs of the late 1990s, when some companies had no revenue, it still harkens back to that time. I've used LinkedIn for several years -- the free version, that is. I love the product, but won't pay for it, and I won't buy the stock either. Pandora Media ( P) came public at $16 a share last June. Nearly one year later, the shares are trading for about $10, down 60%. This Internet radio company's product is outstanding, and I use it on a daily basis -- the free version, that is. I don't mind hearing a few commercials in lieu of paying up. Pandora is not profitable on a trailing 12-month basis, and sells for about six times its sales.