Steve Ballmer had something to say about almost every fashionable technology going in his trademark Washington DC speech, but his sudden enthusiasm for tablets deserves nothing but groans.

As any tablet historian will recall, Microsoft was a pioneer of these devices, embracing the concept as long ago as 2001, years before the celebrated iPad had even made it on to the back of a cigarette packet at Apple HQ. As any tablet historian will also know, they were expensive and hopeless for all but niche users.

Now that another company has done the market legwork, Ballmer's enthusiasm for mass-market tablets is suddenly renewed.  As in 2001, Ballmer still believes, ridiculously, that tablet computers are a perfect fit with Windows.

As any tablet historian will also remember, it was the porting of Windows to tablets that nearly killed the concept all those years ago.

What else can Ballmer say? He has an urgent need  to come up with reasons for the increasingly obsolete operating system concept to exist because it sustains the licensing revenues from a slowly-corroding business model of selling bloatware to users who grew up with PCs.

Windows 7 tablets are bound to be more expensive and complex than ones based on Android or WebOS, which was probably the major reason why HP bought Palm. More recently, Toshiba has put out feelers with its own rather stunning Android device. The Windows-based devices, such as the Asus Eee Pad have looked unconvincing.

Windows was invented for a class of devices, PCs and laptops, that over time fewer and fewer people will use as their primary computing device. The idea that Ballmer can magically shoehorn Windows 7, or perhaps Windows 7 Phone, into such devices without there being tears along the way is suspect at best.

The limitations of the Windows interface and OS for this sort of device could occupy an essay I don't intend to write, but the biggest argument against Windows on tablets is simply the fact that Ballmer feels the need to stand up and say this in 2010. Where was his enthusiasm for tablets in 2009 or 2008 when Apple and others saw the potential to reinvent the idea in a new form?

Microsoft's embarrassing lack of vision is stripped bare by the flawed and expensive iPad. It's as if Microsoft uses companies such as Apple as an unofficial R&D department, inventing and proving ideas it no longer has the confidence to push through. Windows, the albatross.

It's Microsoft's chronic lack of innovation problem is its essence.

Ballmer loves tablets but he'll need something better than Windows 7/Phone for tablet users to love him.