> The problem is digital things don't decay in the same way as physical objects.

I'm not so sure of that. Ask anyone who's ever used VBScript, ActiveX, Flash, <blink>, <marquee>, or (soon) XSLT.

The web likes to portray itself as championing backwards-compatibility, but for better or worse, it is quick to drop technologies perceived as harmful or merely wasteful. If you're unfortunate enough to jump on the wrong bandwagon, you can easily be left behind, and any older pages left untouched can quickly become non-functional.