I know I'm a little late to the party here, but I'm finally starting to see the use case for Site Specific Browsers.
For those of you who haven't used one, an SSB is basically a web browser that's dedicated to accessing pages from a single site or application with a lot of the extras stripped out -- that's right, no location display, toolbar, or menus. Popular examples include Mozilla's Prism and Fluid for OS X (based on Apple's WebKit). You could also argue that Adobe's AIR platform provides an SSB of sorts.
So how does it work? Well, with Fluid, you run the app, it asks you for a name and a URL, and creates a desktop application icon for that site, err, application. You can then click and launch that site directly, as if it were any normal application.
So this sounds pretty crippled, right? Then why, exactly, are they useful? I can think of a few reasons...
First of all they're isolated. If you're like me, when you're browsing the web, for research or for fun, you often have a lot of tabs open. And... sometimes the content of those tabs can destroy your browser session. That's no fun. If you're working with one or more mission-critical apps that you have open all day long, you'd probably like to isolate them from these sorts of issues. So, make a properly segregated 'application' out of them, allowing them to run as their own process. SSBs excel at this sort of thing.
Another commonly cited reason to embrace the SSB is their distraction free nature. If you spend your day doing a lot of work in web apps (perhaps pay-for, subscription-based, etc applicaitons), there's a good chance that you don't want or need a lot of the other extraneous features offered by a browser package -- or the numerous plugins which you've installed (to make your life better, of course!). Sometimes, as they say, less really is more.
If you're a developer of some prosumer web-based application, making that application available as an SSB can even provide an added air of legitimacy to long-time desktop app converts who are seeking the latest and greatest online. Browser-based apps are doing more than most people would have ever imagined in the late 1990s and in many cases have become full-on replacements for the traditional desktop-oriented counterparts -- spreadsheets, calendars, even graphic design packages -- they're all moving online. Still, some of your users may continue to prefer having an icon to click on for easy launching. That's not a problem with SSBs.
Honestly though, one of the coolest uses of this sort of technology that I can think of is on the mobile phone. Like many others, I too stood in line for 3+ hours last Friday to pick up a shiny new iPhone 3g. Ultra-fast Mobile Safari works great and saving and retrieving bookmarks is easy, but sometimes you just want to make a quick-launch icon for a commonly used application. Fortunately Apple worked this into their design.
When you find a web app you like in Safari, tap the plus sign, and then tap the 'Add to Home Screen' button that pops up. The iPhone makes a web clip and adds an icon for it to your home screen. This means you can just select it like any other (non-) web app, and instantly, wham -- there's Google Docs or Remember The Milk.
Of course, this is basically just an implementation of OS X's web clips for the iPhone rather than a true SSB -- you'll note that upon clicking, it literally just pops up a copy of Safari with the appropriate bookmarked URL loaded up.
Does that location bar really have to be there? Is it really that crazy that removing the toolbar and trimming down the functionality could result in web-based apps that feel more like regular App Store purchases? This feels like the perfect place for an Site Specific Browser to me.
What do you think?