Like many people, I’ve been trying to wrap my head around the motivations behind yesterday’s release of Safari for Windows. With iTunes for Windows, it was a slam dunk - you can’t sell iPods and tracks to people who can’t reach your platform. But with Safari, it’s not quite as clear cut. What exactly is Apple selling? Ostensibly, it’s about giving Windows developers access to Webkit, the browser engine that will be running on the iPhone. But I don’t buy that that’s the whole reason. Developers are just too small an audience to warrant the work it must have taken to do the port, and to support it going forward (after all, they could have given developers Webkit without porting the whole browser).

Then there’s the old “gateway drug” argument - give Windows users enough tastes of Mac elegance - and in this case a faster browser than anything available on Windows right now (Apple claims Safari 3 is twice as fast as Internet Explorer 7 on Windows, and 1.6 times faster than Firefox 2) - and eventually they’ll wander over to take a closer look at the whole enchilada. But how many Windows users are going to care? Those who care enough about security and extensibility to try another browser are already using FireFox, and Safari doesn’t have FF’s thriving plugin landscape going for it. Speed alone isn’t going to cut it.

So… Apple is going to end up with a tiny percentage of developers and geeks running Safari on Windows. And this benefits Apple how? I was thinking there must be another shoe ready to drop, lurking stage left. Then I read John Gruber’s notes on the keynote, and it all started to make sense.

“It’s not widely publicized, but those integrated search bars in web browser toolbars are revenue generators. When you do a Google search from Safari’s toolbar, Google pays Apple a portion of the ad revenue from the resulting page. … The same goes for Mozilla (and, I presume, just about every other mainstream browser.) … For example, the Mozilla Foundation earned over $50 million in search engine ad revenue in 2005, mostly from Google. … Apple is currently generating about $2 million per month from Safari’s Google integration. That’s $25 million per year. If Safari for Windows is even moderately successful, it’s easy to see how that might grow to $100 million per year or more. “

So there’s the other shoe. Obviously, Webkit for Windows is essential to iPhone developers, and there’s certainly the possibility of Safari turning a few Windows users onto the Mac. But Safari/Win actually is selling something to the public - eyeballs for Google. And that’s the secret sauce that makes it all worthwhile.