Completely unacceptable to take away user choice over a contract squabble (Anyone who has convinced themselves that this has to do with malware or licensing is naive). Removing the ability to set Bing as default search does absolutely nothing to protect the user. It simply produces a barrier which makes things slightly more difficult, a tactic that sadly will work on many people. Thank you for posting the workaround!
As a long, long time Opera user I'm extremely disappointed in this move. Those of us who think about this even a little bit see through the malware argument. If Bing were truly such a security threat shouldn't Opera warn users who even attempt to visit the page? If the problem were real there would be zero liability in doing so. It becomes even more suspect when you factor in articles such as this which bring into question the validity of the malware claims in the first place:
Bottom line is if Bing is truly a threat we need to protected from then Opera is doing a disservice to its users by not instituting a warning each time the page is visited or better yet, blocking it entirely. If it is no more dangerous than any other search engine, as the article I cited claims, then stop limiting your users by ending this.
On another note, I do see the irony in a company who was once taken to court for limiting its users personal browser choice being placed in the role of victim in a very similar circumstance. 