I'm actually writing this blog post from a Chromebook that I got for attending the Google I/O conference last month. This device is perhaps the logical conclusion of the web apps replacing desktop apps axiom. However, I have a problem with that axiom. It is often based on the emergence of popular websites like Yahoo, Google, Amazon, and eBay. The argument is that these apps were web based and the fact that they ran on servers that could be rapidly updated is a key to why they succeeded. The long update cycle of desktop software would have made it impossible for these apps to be anywhere but in a browser.
There is some truth in this, but it's misleading. The most important factor in the success of those apps was that their data was in the cloud. They brought information and interactions that could not exist simply as part of a non-connected desktop app. They had business models that were not based on people paying to install the software. These were the keys. The fact that end users interacted through a web browser was secondary. It's pretty much the same story for newer super popular web apps like Facebook and Twitter.
Going back to the world of mobile for a minute... One of the things that mobile has taught us is that users don't care so much about how they interact with your "web-based" application. Hence the popularity of native apps for web giants like Amazon and Facebook. In fact, some might even argue that users prefer to use native apps to interact with traditional web properties. I won't argue that, but I would definitely disagree with any claims that users prefer to use a browser.
Anyways, the point is that the notion that web apps replaced desktop apps is dubious. In fact, if you look at places where web apps were tried to exactly replace desktop apps, such as word processing, they have had limited success. Currently we see a movement to replace music players like iTunes with web apps. These web apps have some distinct advantages, but it is not at all clear that they will prove popular with users. Apple has taken the approach of adding more network based features (store and download your music from their servers) to iTunes instead of going with a web app -- at least for now.
Connected desktop apps have a lot to offer. I often find myself using desktop apps like Twitter, Evernote, Sparrow (for GMail), and Mars Edit (for Blogger.) They provide a better experience than their browser based cousins. Apple's Mac App Store has definitely made such apps more popular on the Mac platform, as they have made it easier to discover, purchase, and update such apps. Speaking of updates, these apps update frequently, usually at least once a month. Again, I think that our expectations have adjusted because of mobile apps.
So will desktop apps make a comeback? Are mobile web apps doomed? I don't know. I think it is very unclear. It's not a given that a computer like this Chromebook that I'm using is "the future." We can haz network without a browser.