I sat in on a meeting with the IT department of a large company. The head explained that for web browsing they had two rules: 1) Only through a portal (kind of understandable), and 2) The only accepted browser was Internet Explorer (and this was two years ago - not even MS recommended that). After carefully mentioning that IE wasn't really considered a secure browser these days it was explained that yes, it was very secure, and the reason was that it was very configurable. Nothing was said from this side after that.