Every 10 years, Microsoft informs its programmer community that it's radically changing platforms. In the early 1990s, it moved developers from DOS-based APIs to Win32 by forcing them through a painful series of API subsets: Win16 to Win32s and Win32g to Win32. In the early 2000s came the push to migrate to .NET. Now comes a new migration to Windows 8's constellation of new technologies under name "Metro".

At least the migration from DOS to Win32 had compelling motivators: a GUI interface and a 32-bit operating system. The migration from Win32 to .NET had a less obvious benefit: so-called "managed code", which in theory eliminated a whole class of bugs and provided cross-language portability. It's not clear that the first benefit warranted rewriting applications, nor that the second one created lasting value.

The just-announced Window 8 technologies are for writing "Metro" apps. Metro apps have a wholly new UI derived from Microsoft's mobile offerings and intended to look like kiosk software with brightly colored boxy buttons and no complex, messy features like dialog boxes.

Bottom line, the costs of these past migrations have been enormous and continue to accumulate, especially for sites that, for one reason or another, can't migrate applications to the new platforms.