I think ChromeOS could succeed in "kiosk" situations -- libraries, coffee shops, hotel lobbies, etc. Verified boot and automatic updates would be a boon for maintenance concerns, while customers would be much more likely to trust Google than a random Windows kiosk with a shoddy browser and questionable shell.
Of course, kiosks / public access terminals may be as unnecessary as phone booths once we're all carrying personal tablets...
There are a lot of people outside of the 1st world's lavish lifestyle and deep pockets (filled also with $500 gadgets). If you live in the USA you don't even have to leave your own country to see the other side.
Strike the last sentence and I agree with your comment wholeheartedly.
Interestingly, outside the "1st world" mobile phones are quite common. The speed at which this technology trickled down is amazing, about ten years from yuppies in major cities to subsistence farmers in failed states. Even more amazing is penetration. Most things just don't go that far down the economic ladder at all. Basic, fundamental things like vaccination, artificial fertilizers, electricity or regular phone lines which our grandparents took for granted have been outpaced by mobile phones in many places.
Tablets may be similar enough to mobile phone to hope that the same economics apply and we might see the <$3-a-day majority benefiting by 2020. Hopefully.
I hope Google will bring Android to the notebook/desktop, make it a rich platforms so that we can finally have Photoshop running on Linux. I'm guessing this is probably the direction: Apple has the same OS code base for phone, tablet and desktop; Microsoft is trying the same with its porting of Windows to ARM processor, targeting tablets.
Conceptually I still like the IDEA of ChromeOS more but I just can't see a consumer choosing what is essentially a browser over something like this.
My only hope is that Google will try and move Android to a place where Web Apps are just as powerful as native apps on the platform.