Tech bloggers and analysts had a collective cow yesterday over the news that January 2008 comScore data suggest clicks on Google’s paid search ads have stopped growing, which implies that Google may be vulnerable to a US recession already underway. Fred Wilson had a sober reflection on why he stands behind his (albeit ill-timed) purchase of GOOG and why he will continue to buy GOOG, arguing that Wall Street has not yet been able to value all of Google’s potential growth opportunities beyond paid search.

Here’s why I think it would actually be, from a long-term perspective, good news if Google proves vulnerable to a recession and a cutback in ad spending — it means Google is a REAL business.

Remember back in 90s when everyone argued that the New Economy wasn’t subject to the same cyclicality as the Old Economy? That New Economy companies were recession-proof? Well, you know how the story ended. The New Economy companies didn’t just slump with a cyclical downturn — they vaporized — poof.

Why? Because they weren’t real businesses.

If Google’s paid search business continued to grow during a recession, during a period of rational pullback by consumers who click on ads and business that pay for those clicks, what would that suggest about Google’s business?

Bubble. Irrational exuberance. Pick your buzzword.

Any business that operates based on cyclical inputs — i.e. consumer spending and ad spending — that appears immune to cyclicality is defying the laws of economic gravity. And when gravity kicks in, it’s not like water rolling down a hill — it’s like Wile E. Coyote realizing there’s no more cliff underneath him.

If Google’s paid search business turns down when consumers and businesses spend less, it makes it far more likely that these consumers and businesses are making rational decisions about paid search advertising — that there is real value there.

Google may slide along with the economy, which is bad news for short-term investors. But it’s good news for long-term investors because it makes it much more likely that when the economy recovers (whenever that is), Google’s paid search business will respond as positively to a resurgent economy as it did negatively to a downturn economy.

It also remains to be seen the response from advertisers who are managing their Google search advertising as a profit center rather than a cost center, i.e. advertisers who can calculate that they get more than $1 back for every dollar they spend on Google search ads.

If you can calculate the profit margin on some of your ad spending, when times get tough, aren’t you more likely to put MORE money into the advertising that you know to be profitable — and do so perhaps by shifting dollars out of the advertising that is of more speculative value, e.g. TV brand ads? Or at least until the profitable advertising ceases to return a profit?

And if Google is indeed a bellwether of online advertising, and it online advertising is rationally tied to the economy, it’s also much more likely the online advertising will accelerate its growth even more when the economy eventually recovers.