There's been a bit of commentary of late regarding Google's recently announced Chrome OS and how it relates to Android. Specifically, Anil Dash and John Gruber question the wisdom of producing two distinct OSes. Anil Dash writes, Google's Microsoft Moment:

This is one of the simplest and most obvious examples, after this week's announcements: Google is now offering not one, but two mobile operating systems. While they undoubtedly share code, I can't help but think back to ten years ago, when Microsoft was vehemently protesting about how much code was shared between the Windows NT/Windows 2000 operating systems and the Windows 95/98/ME operating systems. If I make a screen two inches smaller, should I use Android instead of Chrome OS? If the keyboard works with my fingers instead of my thumbs, I should use Chrome OS and not Android? I know Google is convinced its employees are smarter than everyone else in the world, but this is a product management problem, not a computer science problem.

John Gruber adds:

It makes no sense to me why Chrome OS isn’t based on Android. Maybe there’s a good answer to this, but Google hasn’t given it.

The obvious answer is that the user's needs, tasks, and interaction methods are so completely different at the two ends of the device spectrum (desktop PCs at one end and small handheld devices at the other) that it's smart to make two distinct operating systems for these classes of devices. Microsoft is an inept comparison in this instance because they've created the worst of all possible worlds: a mobile OS that has completely different underpinnings from their desktop OS, while still carrying over so many desktop interaction and visual design patterns that aren't suited for handheld tasks. Windows Mobile isn't well designed for short-duration tasks, ancillary tasks (while you're doing something else and your handheld is playing a supporting role), or 'tiny fingers' tasks. Saying two OSes is a bad idea because Microsoft did it is not a powerful argument. So let's turn to Apple. They currently have three distinct OSes: Mac OS, the iPhone OS, and the iPod OS. Let's leave the iPod OS out of this discussion because its feature set and intended utility is such a small subset of the other two that it's unreasonable to include it. Both the iPhone and Mac OSes share a lot of code and lower-level architecture. They're both 'based on OS X' though that distinction means nothing to the end-user, as those similarities don't carry over into the experience using the devices. The common infrastructure helps with porting code and smoothing the learning curve for iPhone developers (presumably) but at the end of the day these two OSes still present the same dilemma that Anil raises: If Apple creates a netbook-style device, should it run iPhone OS or Mac OS? Of course, Apple will choose one way or the other, while the Acers and Dells of the world will probably choose both, but the dilemma is a false one. The two OSes are created for different styles of interaction, so at the end of the day you-the-consumer are looking for a product to meet your portable, ancillary support, quick-use fingertip device, of you're looking for a focused-attention computing platform in as small a form-factor as is usable. To say that there should only be one Google OS merely because there exists an overlap in the desired form factors for two distinct OSes is as silly as the idea of an iPhone running MacOS or a Mac with the UI of an iPhone.