The free-for-all continues. Amazon.com has opened up its Alexa search engine to all comers. Just as Amazon’s affiliates can tap into the company’s merchandise catalog to build their own stores, so entrepreneurs and tinkerers can now tap into Alexa’s vast catalog of web content to build their own applications or sites. And, for modest fees, they can even use Amazon’s computing platform as their own computing infrastructure. Just plug into the utility socket.

John Battelle, who broke the news, sees this as a potential “game-changer” in the search world. Om Malik sees it as a commoditize-thy-enemy’s-product tactic: “Amazon.com is trying to inflict death by a thousand cuts to rivals including the GYM Gang” – ie, Google, Yahoo, Microsoft. Phil Wainewright calls it – gulp – “a seminal moment in the dawn of Web 3.0.”

Whether Amazon’s looking to make money or make it harder for rivals to make money, the move does look like something of a watershed. What’s interesting is that it separates, or unbundles, the “engine” that, in a real sense, powers the web from the applications of that engine. And it turns the engine into a cheap commodity. It’s not hard to think of what happened when another engine – the steam engine – became a commodity a couple hundred years ago. An incredible number of applications of steam power were rapidly invented. Now, the search engine is far from the steam engine, but the example shows what can happen when you commoditize a basic piece of commercial infrastructure, giving a lot of people and companies access to it. The big question is: Are there a whole bunch of incredibly valuable search applications to be invented, or will this just set off an explosion of cute mashups? We’ll see.

One other thing’s worth noting: This promises to add yet a few new wrinkles to the confusion surrounding copyright and intellectual property on the internet.