And your point is what exactly. That Google is far more diversified with its income than Facebook. That Google doesn't break out Google+ P/L so we can't do a direct comparison. That search advertising has different dynamics to social advertising.
I mean did you also want to compare Facebook with Exxon Mobile or Starbucks ?
The way that valuation of a company works is that the multiple of market cap over annual revenue is supposed to reflect (mainly) expectations of growth. This multiple for Google is less than Facebook's by a LOT, because Google, as a relatively mature company working off of a larger revenue base, is expected to grow more slowly percentage-wise, all else held equal (this has been borne out by the vast majority of companies, and is pretty much common sense, as doubling sales is a lot harder to do when one is already doing tens of billions of dollars in sales).
The fact that Facebook is growing more slowly than a company with much lower expectations of growth instead of living up to its expectations of hypergrowth (as implied by the valuation) is a signal that the current growth expectations (as implied by the valuation) are too high (hence the "all else held equal" part of the last paragraph: if a company isn't performing as well as it should, then it's of course possible that it'll grow more slowly than a larger competitor with lower expectations of growth). This of course ignores the possibility that FB comes up with an amazing revenue-boosting innovation like AdWords and begins to fulfill their expected growth rate.
Things like "search advertising has different dynamics to [sic] social advertising" can't just be completely removed from consideration. They're precisely what determine if Facebook is inaccurately valued or if the huge growth expected from it will occur/continue.
Google is a direct competitor to Facebook when it comes to Ads. It doesn't really matter if the advertising is search based or social. They are vying for a piece of the same pie.
The really high valuation of Facebook is partly because investors expect it to grow substantially, at least in the short term. The fact that it's growth is lower than that of it's direct competitors (who have a much lower P/E) is not a good sign for the stock in days to come.
But again. Google is diversified beyond just advertising whilst Facebook isn't. It seems illogical to just blindly compare total revenues.
Why not compare Facebook/Google to Apple then since they are also vying for the same piece of the pie ? Or News Corp ? Or Vogue magazine ? Or Playboy ?
I mean did you also want to compare Facebook with Exxon Mobile or Starbucks ?