Google. If Google is not thinking in terms of the above, I will eat danah's furriest hat. They've already shifted the focus of Google Desktop with the addition of Sidebar and changing the name of the application (it used to be called Google Desktop Search…and the tagline changed from “Search your own computer” to the more general “Info when you want it, right on your desktop”). To do it properly, I think they need their own browser (with bundled Web server, of course) and they need to start writing their applications to work on OS X and Linux (Google is still a Windows company). Many of the moves they've made in the last two years have been to outflank Microsoft, and if they don't use Google Desktop's “insert local code into remote sites” trick to make whatever OS comes with people's computers increasingly irrelevant, they're stupid, stupid, stupid. Baby step: make Gmail readable offline.
In agreement, Gmail with offline support via google desktop would be a good move forward.
Yahoo. I'm pretty sure Yahoo is thinking in these terms as well. That's why they bought Konfabulator: desktop presence. And Yahoo has tons of content and apps that that would like to offer on a WebOS-like platform: mail, IM, news, Yahoo360, etc. Challenge for Yahoo: widgets aren't enough…many of these applications are going to need to run in Web browsers. Advantages: Yahoo seems to be more aggressive in opening up APIs than Google…chances are if Yahoo develops a WebOS platform, we'll all get to play.
Hard to admit, but Yahoo are seriously getting this and have over took google in the innovation field. Yes Google still have the upper hand, but I'm not certain that will be the case if Yahoo do buy Technorati or launch there killer. I'm also thinking Yahoo and Mozilla could partner if Jason is right about Widgets not being enough.
Microsoft. They're going to build a WebOS right into their operating system…it's likely that with Vista, you sometimes won't be able to tell when you're using desktop applications or when you're at msn.com. They'll never develop anything for OS X or for Linux (or for browsers other than IE), so its impact will be limited. (Well, limited to most of the personal computers in the world, but still.)
I'm still trying to get my head around a operating system which is so web enabled. I'm assuming RSS will allow Vista to by pass the web on the desktop type crap. Hopefully Microsoft have got there thinking hats fully on because they will miss the trick if they let Yahoo and Google develop a web OS on top of Vista.
Apple. Apple has all the makings of a WebOS system right now. They've got the browser, a Web server that's installed on every machine with OS X, Dashboard, iTMS, .Mac, Spotlight, etc. All they're missing is the applications (aside from the Dashboard widgets). But like Microsoft, it's unlikely that they'll write anything for Windows or Linux, although if OS X is going to run on cheapo Intel boxes, their market share may be heading in a positive direction soon.
I think Apple get it but there hardware/software dependancy is a problem which could really slow them down. I expect we shall see what happens with the whole Apple on Intel deal.
See I think Jason has it a little wrong here. Mozilla has built a lot of community mind share into there web OS products. More so that the others in some respects. Also about the small web server, Greasemonkey anyone? XUL runner is also the foot in the door of widget type fuctionality and they certainly have the full support of the community behind them. How many extensions are there now for Firefox, anyone? Jason also made reference to the lack of rich UI support in web OS. Well Mozilla's got the open standards message and is using SVG, XBL and other standards going on. My bets are on Mozilla and Yahoo for sure.