I don't know how this failure happened, but I'm certain it wasn't intentional. IE market research has been tracking the effect of the browser ballot closely and found it to be almost completely negligible - the people who don't pick IE from familiarity / brand recognition are the same people who would have downloaded another browser anyway. They wouldn't have risked another legal/PR/financial fiasco over that. I'd really hate to be whoever's responsible for whatever snafu was the immediate cause ...