Exchange traded funds offering exposure to social media have been the toast of the town this year due in large part to Facebook’s (NasdaqGM: FB) resurgence and Twitter’s (NYSE: TWTR) recent initial public offering.

The Global X Social Media Index ETF (NasdaqGS: SOCL), the lone dedicated social media ETF, has surged 50.3% this year while the First Trust US IPO Index Fund (NYSEArca: FPX) has soared almost 38%. Following the Twitter IPO, the stock is down nearly 6% in the past week, some caution may be warranted when it comes to social media and IPO ETFs.

“Twitter had 232 million monthly active users around the world as of September 2013, posting some 500 million tweets a day. As impressive as that user base is, Facebook’s is even bigger, with over 1.2 billion monthly average users that had over one trillion connections and shared over 240 billion pictures. While social media is not a major business for Google (NasdaqGS: GOOG), with Google+ we think the company is a leading global player in the category, with a recently indicated 300 million active users,” said S&P Capital IQ in a new research note.

Although S&P Capital IQ Scott Kessler, an equity analyst for S&P Capital IQ, thinks Twitter has substantial revenue growth potential, given what he sees as a notable multinational brand and user base, emerging monetization efforts, and strength in mobile, he has a two-star, or sell rating, on the shares.

Twitter of was added to SOCL last week at a weight of 4.5% and to the new Renaissance IPO ETF (NYSEArca: IPO) at a weight of 2.44%. Despite a large loss for Twitter on Monday, the two ETFs have traded higher over the past five days. [Twitter Enters IPO ETF]

FPX, IPO’s older rival, does not yet hold shares of Twitter, but FPX’s largest holding is Mark Zuckerberg’s Facebook at a weight of 10.4%. IPO features a 9.8% weight to Facebook as does SOCL. S&P Capital IQ has a three-star rating on Facebook. [Facebook Boosts Social Media ETF]

“Kessler, who also covers FB shares for S&P Capital IQ, sees 40%-plus revenue growth for Facebook in 2013 and 2014, tied to advertising, and sees earnings growth also from operating margin expansion. That said, based on a P/E and P/E-growth basis, he thinks the valuation is reasonable at current levels and does not recommend purchase of the shares,” according to the research note.