>Companies have far too much internal plumbing to permit browsers to auto-update themselves. Being feature-compatible with the latest SV-poster-child website is insignificant compared to maintaining stability for the tax-management team's internal web app.

So why don't they have two browsers - one for internal use only (IE6), which is firewalled to only internal network shares and another browser (Chrome, whatever) which can only go to the real internet?

At least that way you'll be browsing the wild internet safely.