Microsoft and Yahoo have finally reached the inevitability of a deal to work together.

As soon as the software giant tried to buy its internet rival something was always going to happen. There might be a few investors still shaking their heads at spurning a buyout at $33 per share last year with Yahoo stock currently below $16, but give credit to the new leadership at what used to be called “the search firm” for convincing shareholders of the long-term value – it makes a change not to be driven by short-term quick returns.

The deal confirmed today means that Yahoo is no longer a search firm – it is an internet firm that uses Microsoft’s Bing search technology. Equally, Microsoft is no longer a search advertising firm – it effectively hands its search properties to Yahoo to do the sales on its behalf.

So what’s it all about?

Putting aside the headline justification – that only a single, combined search engine can really compete with Google and attempt to claw back some of the billions of ad sales not going to Microsoft/Yahoo – perhaps Redmond still thinks it can apply some of what it has learned from the past into the future of the web.

This could be Microsoft’s attempt to commoditise search – in which case, we might start to see “powered by Bing” appearing more frequently around the internet.

Microsoft – despite its protestations to the contrary – has never really been an innovator. It is a close follower; it takes other people’s ideas and turns them into big-earning commercial products. The firm has commoditised operating systems, wordprocessing, spreadsheets, browsers and so on, and through Microsoft’s sheer scale has knocked out rivals that depended on a high ongoing licence stream.

Such a strategy is not unlike what Google wants to do to Microsoft, but by making many of those applications available for free on the web.

Some experts say that Google is pursuing classic disruptive marketing techniques by building products that in future can obviate the need for Microsoft – for example, if the world moves to Android-based smartphones and Chrome OS-based netbooks instead of Windows-based PCs.

But Microsoft is the past master at market disruption.

Remember that Google is entirely dependent on online advertising – mainly search based – for its revenue. If a rival can commoditise search technology, make it so ubiquitous that it has no inherent value, and support it by driving down advertising rates as a result, then who takes the biggest hit? Google, that’s who.

I’m very hesitant of seemingly going overboard in making the future of IT appear to be about nothing more than a battle between Google and Microsoft. Clearly their rivalry is going to be a major issue for years to come, but there’s a lot more to the IT world than those two giants.

And as I have written before, it will take a lot more than the Yahoo tie-up to make people want to Bing rather than to Google.

Nonetheless, Microsoft is smart enough to realise how the world is changing, and to recognise that the company that has become most associated with that change is still dependent on one – albeit currently very healthy – income stream.

Disrupt that stream, and Google’s ability to disrupt takes a big blow.