It seems like someone who makes decisions for DivX got a bit greedy. I am curious why Bing though? It seems to me like all the shady "Install this too?" dialogs are for Bing toolbars and such.
Google [1] and Ask [2] isn't better either, they are offered with most updates of Adobe Flash and Java. Guess everyone will sneak something in if given the opportunity.
Sorry I am not following you. Are you trying to say its okay to bundle/install 3rd party products that are considered good/acceptable? If so keep in mind humans have different tastes, what maybe considered good by you or me may not be by others. It is considered unethical to bundle programs since the days of Bonzi Buddy.
I think Bing is more willing to spend money to get traffic. You can easily get $5 a month in Amazon credit from their rewards program just by using Bing. They have a few other interesting promotions, such as starbucks cards and XBox Live Gold membership. But I'm sure this is costing them a decent amount of money.
I guess you never had random apps offer to install Google Chrome and make it default browser (which I consider being spyware wrt non-tech-literate users).
[1] http://i.imgur.com/5mAdH.png [2] http://i.imgur.com/3zWPK.jpg