Gauging the valuation of private companies can be tough, but that hasn't stopped investment bankers from drooling all over themselves as they look ahead to potential multibillion-dollar IPOs in the social-networking space. Heck, Wall Street even has its own self-proclaimed social-media analyst now, in Lou Kerner. Brilliant! These guys are all over this trend.

We've seen some big numbers thrown around for the likes of Facebook, Twitter, Groupon, Zynga, and LinkedIn. Zynga's value has been pegged around $10 billion, well beyond traditional gaming powerhouse Electronic Arts (Nasdaq: ERTS), while Groupon thinks it's worth considerably more than the $6 billion that Google offered.

And then there's the king of all social media -- no, Rupert, not News Corp.'s (NYSE: NWS) soon-to-be-former debacle, MySpace -- but Facebook, which has seen valuations in the $80 billion range.

Berkshire Hathaway (NYSE: BRK-A)(NYSE: BRK-B) head honcho Warren Buffett apparently won't be among the buyers when these companies go public. He's said that "it's extremely difficult to value social-networking-site companies" and that "most of them will be overpriced."

But let's face it: He's old and probably wrong.

To help Wall Street show Warren and the other doubters why these companies are worth going gaga over, I've come up with a few handy valuation metrics.

Price-to-Friends. Forget focusing just on users. With Facebook and other social-networking sites, we're going to focus on friends. Facebook has around 500 million users, and each user has around 130 friends, so there are currently 65 billion friends on Facebook. Value each friend at oh, say, $5, and Facebook is worth $325 billion. Count me in!

Price-to-Tweets. Is there a clear value to a tweet on Twitter? No, but there could be, right? According to The Huffington Post, Twitter currently handles a billion tweets per week, and daily tweets have grown from 50 million to 140 million in the past year alone. With that impressive 180% growth at its back, we have to at least put a multiple of 5 on current tweets. That would give Twitter a valuation of $260 billion. Now that's worth retweeting.

Price-to-Levels. On Zynga games such as FarmVille and Mafia Wars, players advance by achieving higher "levels." I've estimated that roughly 50% of my Facebook friends are on at least one Zynga game, which would mean that around 250 million of Facebook's total users are playing Zynga games. After a short stint on Mafia Wars last year, I'm at level 128. Assuming most users have reached just this low level, we're looking at 32 billion levels. With a price-to-level multiple of just 8, we've got a $256 billion valuation for Zynga. Plant that in your farm, you naysayers!

I'm sure there are plenty of other Fools who'd like to help Wall Street value these social-media companies, so go ahead and share your valuation techniques in the comments section below.

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Fool contributor Matt Koppenheffer owns shares of Berkshire Hathaway but of no other companies mentioned. See what Matt's keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.