We know software vendors had been abusing our trust in them with automatic update mechanism. Apple is the worst case reported when it push Safari to windows users via iTune update.
Initially, I did not know Microsoft use its update mechanism before to push third party software. Therefore, when I read this article about lawyers for a class action suit wanting the judge to get Microsoft to post court notices via its update mechanism, I thought it was novel use and a very cost effective one but unfortunately for the lawyers, Microsoft will say it is only used for updating its own software and doing what the plaintif wants will compromise the integrity of the system and that excuse might fly. However, now that I know Microsoft did carry third party traffic, I think it is Microsoft that is going to have a much tougher time defending it.