It was one of those television moments when my mouth began filling dead air before my brain could catch up. I did sprinkle some context around the line, about how Facebook and Google (GOOG) were both “once in a tech generation” outliers, but it remained something that gnawed at me after the red light switched off.

Basically, Facebook is not Google. Yes they are both wildly-popular Internet companies whose IPOs have been hyped more than The Avengers vs. Avatar. Yes they are both led by folks who sometimes forget that privacy is more than just a passing fad. But, no, they are not really comps when it comes to their initial public offerings.

Google went public in August 2004, which was six years after being founded. At the time, it had raised just around $30 million in venture capital funding, had around $1.35 billion in annual revenue and nearly 2,300 employees.

Facebook, on the other hand, has been around 33% longer than was Google at the time of its IPO — having been founded in February 2004. It has raised over $2 billion in venture capital funding (depending on how you count it), has around $3.7 billion in annual revenue and over 3,500 employees. The social network also has been at the vanguard of private secondary market trading among both its employees and investors, something that Google never had to deal with.

In other words, pre-IPO Facebook is much more mature than pre-IPO Google. It has lived more, seen more, dealt with more people and handled more conflicts. It has come of age in an era of increased media scrutiny — something enabled, ironically, by social media sharing that Facebook itself helped popularize.

None of that necessarily makes 2012 Facebook better or worse than 2004 Google. Just different.

So should it really worry prospective investors that Facebook’s revenue growth slowed more over the past year than did Google’s in 2004? I keep reading that it should, but doesn’t it stand to reason that an older company’s growth curve would have flattened a bit more than that of a newer company. Should investors worry that Google felt fresher in 2004 than Facebook feels today? Not if you take the term literally. Or if you realize that Google was pricing at a time when the general public was unsure about the viability of Internet businesses, compared to a 2012 environment in which Congress feels compelled to help everyone get in on the craze.

Facebook should be judged on its own merits at IPO, not against an anachronism. It may be a tougher exercise, but no one ever said investing is supposed to be easy.

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