Google (Nasdaq: GOOG) never really stopped growing during the recessionary downturn that claimed most of its online advertising rivals. With sentiment improving, why would it buckle now? That's right -- the world's leading search engine delivered another monster quarter.

Revenue before traffic acquisition costs soared 24% to $5.06 billion. The bottom line grew even faster, with non-GAAP earnings surging 31% to $6.76 a share. Analysts figured that Google would earn just $6.60 a share without cracking the $5 billion revenue mark, but then, they've been serial lowballers. Google has topped Wall Street estimates in each of the past seven quarters.

Good news turns into great news when one considers that Google's number of paid clicks rose by 15% during the period. See how revenue grew even faster? That's refreshing. It means that advertisers are paying more for every lead that Big G delivers (in this quarter's case, 7% more than a year ago).

The market jabbed the stock on the news, but that's not Google's fault. After such a great report, and heady gains over the past year, the stock is simply taking a breather.

This doesn't mean the news was perfect. I want to point out a metric that I doubt any other analyst even cares about. But they should.

Google generated $2.04 billion in revenue from its AdSense partners, paying them $1.45 billion -- or 71% -- of the money generated by populating their sites with targeted AdWords blocks. I realize that 71% is a very generous cut, but a year ago, Google paid $1.23 billion to its network partners during the same quarter, or 75% of the $1.64 billion in related revenue. Go back to the first quarter of 2008, and Google ultimately paid AdSense partners $1.34 billion, or 79% of the $1.69 billion it collected from their sites.

This may not seem like a problem to you. Google is simply squeezing more money out of its AdSense program, a savvy margin-pumping move in a vacuum. What about the other side of the equation, though?

Publishers have seen their sites generate a 21% spike in Google revenue over the past two years, yet their proceeds have only grown by 8%. Will they get up and go elsewhere?

Don't bet on it. Yahoo! (Nasdaq: YHOO) recently shuttered its AdSense clone.  Microsoft's (Nasdaq: MSFT) pubCenter is still in beta, and largely unproven.

AdSense publishers don't have much of a choice, and they're not exactly complaining. AdSense sites generated a 24% increase in revenue for Google over the past year, better than its organic 20% jump for company-owned sites.

Google can also argue that 71% today is better than 79% two years ago. It has a deeper sponsorship pool, and advertisers are now paying more per click on average.

Still, this could be a golden opportunity for Microsoft, if it's able to build up its ad inventory. It also makes one wonder why Yahoo! decided to axe YPN instead of sweating it out, given the outreach opportunities resulting from Google's diminishing payout trend.

Is Google's program just too ubiquitous? Even high-volume sites including AOL (NYSE: AOL) and News Corp.'s (NYSE: NWS)(NYSE: NWS-A) MySpace have turned to AdSense in the past, when they, too, would seem like natural candidates to build AdSense rivals.

Investors don't have to worry about this for now. As long as there is no legitimate AdSense competitor, and network revenue continues to grow, the shrinking partner payouts are a testament to the elasticity of Google's program. However, you may as well bone up on the trend now -- before everyone else is talking about this in a year or two.   

Can anyone seriously take on Google's AdSense juggernaut? What did you think of Big G's quarterly report? Share your thoughts in the comment box below.