Put up a terms of use or force users to accept a license agreement. They do no such thing today. So I think you'd have a hard time saying Microsoft has done anything legally wrong here.
5.3 You agree not to access (or attempt to access) any of the Services by any means other than through the interface that is provided by Google, unless you have been specifically allowed to do so in a separate agreement with Google. You specifically agree not to access (or attempt to access) any of the Services through any automated means (including use of scripts or web crawlers) and shall ensure that you comply with the instructions set out in any robots.txt file present on the Services.
In this case I don't think Microsoft violates Google's TOS because it is not directly consuming the "service" provided by Google, but rather peeking at what the user has done (and by installing the toolbar the user has already agreed to let Bing do it).
Imagine the Google terms of service said, 'Users must not share any information we provide with anyone else'. Does that mean that use of the Microsoft toolbar would violate these terms and Google could sue Microsoft to stop them using the 'clickstream' data?
They've done as much legally wrong as bundling IE with windows.
It's most certainly morally wrong.
I want to see a project started to r/e the bing toolbar, and create something to send rubbish data back to bing to screw up their search index. That'd be awesome to see.
