Investors imagine a big payoff from social-media stocks!

Investors imagine a big payoff from social-media stocks, spurred by the hot initial public offerings of social-media stocks such as Groupon (GRPN, Trade ) and LinkedIn (LNKD, Trade ). They're expecting to cash in whenever Twitter, Facebook and others go public.

Then there are the plays such as Nutrisystem and Google that maybe touch on social media but aren't necessarily social media stocks. For someone looking for a pure play on social media, part of the idea is that all stocks in the sector should benefit when a popular company like Facebook goes public and makes a big splash. It's hard to see how or why Nutrisystem makes the connection (having cool apps probably should not be enough), or how the social-media component of Google will move the giant stock.

Google, one of the top 10 holdings in the Global X fund, also highlights another fundamental concern for investors -- while they can't necessarily get a pure play on social media companies, they'll find issues like Google and Sina in plain-vanilla technology funds. That kind of fund will be less volatile than a niche issue.