Last week, I pondered Adobe's big push to position Flash as a platform for mobile devices. It's facing an uphill battle, particularly when it's forced to compile Flash apps down to native binaries to get them to run on the iPhone. Open Web standards seem like a much better development target for today's smartphones -- but not even the mobile Web is a sure bet. The problem, in a nutshell, is scalability.

When developers talk about scalability, they're usually talking about scaling up. That is, when confronted with an ever-increasing load, can the application make efficient use of all the available resources to meet the demand? Web applications have always been pretty good at this (when they're coded properly), and modern advances are making them better.

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Throw mobile into the mix, however, and developers face a whole new challenge. Now their applications need to be able to scale down, too -- to deliver the nearest-possible equivalent to the desktop experience on devices that lack processor power, screen resolution, network bandwidth, and storage capacity -- all at the same time. That's a tough nut to crack -- not just for runtimes like Flash and Java, but for Web standards-based applications, too -- and it's getting harder all the time.