Two interesting articles came up on .net magazine yesterday: "My websites will only support the latest browser versions" by Aral Balkan and a counter piece "Develop for as many users as possible" by John Allsopp.
Balkan makes a fairly convincing argument about the ease and automation of upgrading browsers, but focuses on designing/developing for browsers. I'm more convinced, and agree, with Allsopp that sites are for people, not for browsers. I think he nails it with:
And however ideal it might be that our users use only the most up to date version of a browser, it simply isn't, and never will be, a practical reality.
Some users don't, can't, or won't upgrade their browser. Some aren't aware that there's a choice available.
Balkan's article also seems to be fairly desktop-focused. Mobile access via feature phones in Africa is booming. These users certainly aren't using the latest and greatest browsers, but that doesn't mean we shouldn't consider them in the design and development of our sites.