I sometimes wonder if Microsoft actually tries to fail before they get started. Seriously, leaving the only default search engine to their own, is as stupid as calling in the bad press early due to lack of long term thinking. Microsoft, say it with me. Choices.
Being as you are incredibly late to the game (again) with a modern smart phone release, you’re not in the position to ask people to Bing it or leave. The very idea only again proves that Microsoft’s thirst for control is going to be their undoing. This is not to say that Google isn’t just as bad. Only Google beat Microsoft out to the market with phones worth owning by MONTHS AND MONTHS.
The smart money for Microsoft here instead would be to include lesser known search options, along with Bing. Making Bing the default is fine, but adding in other smaller players will go a long way to keeping people from coming to Redmond with torches looking for the Windows Phone 7 beast.