To make this argument, Hough compares Facebook to Google (GOOG) a few different ways. One view: Google trades at 3.6 times its projected revenues for 2014. Analysts expect Facebook to have $8.2 billion in sales that year, so assuming Facebook has about the same price-to-sales ratio, it would be worth $29.52 billion.

GOOG Price / Sales Ratio data by YCharts

Another view: to be more conservative, look at Google’s price to trailing revenue.

With Google trading at 5.1 times revenue, and Facebook’s trailing revenue at $4.5 billion, that’s a market value of $22.95 billion. (Hough calculated $22 billion.) And obviously, that’s just over half what the market says it’s currently worth.

But is it even worth that? When you use Google, you enter a search term, and Google gives ads relevant to that search term. I type “opera” into Google, and in addition to the search results, it suggests a site to download opera music and a local opera theater. Facebook ads, meanwhile, aren’t as well targeted. In fact, they struck us here as pretty far off-base, and Facebook seems to be rethinking its ad strategy.

As is, Google should be able to charge more money for its ads than Facebook can get. In that case, Facebook’s market value should show an additional discount. What’s that bring it down to, $15 billion?

FB Market Cap data by YCharts

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