For about two years, Microsoft has been battling a lawsuit by a useless piece of slime company called Eolas, which claims that it holds a patent to something running in a web page automatically. Somehow, this does not count as obvious. Anyway, the courts have upheld the patent despite the entire rest of world+dog thinking they are full of it.
Well, Microsoft has decided to change IE as a result. An eWeek story covers the change in a high-level way, with MSDN hosting an article, "Activating ActiveX Controls", which explains that users will need to activate controls in a web page for them to run. Now, in a way, this may assist in security, because users will need to request a page to do something before it does it. However, the basic expectations of the user community are now broken. When a user goes to a web page, they expect the Flash animations to run, the media to play, and so on. They don't expect to have to activate the media element first.
Following this through, this would mean the same thing would be needed in Firefox, Opera, etc., so this is not an IE-only situation. The original patent covers the Netscape plug-in model as well.
Thanks, Eolas, for being a despicable company with no moral center and no worthwhile values.