It was installed by the OEM. Doesn't really help if it only notifies the OEM.
> (2) Microsoft. Do their license terms really allow OEMs to install MiTM proxies and screw around with the root certs? Microsoft could do a good thing here by disallowing this sort of malfeasance... or is there some problem I'm not seeing with such an action?
The general solution to what you're talking about is to prohibit the OEMs from installing anything by default. The problem is the OEMs wouldn't like it and Microsoft has to keep the OEMs happy lest they get any bright ideas about offering their computers with Ubuntu for $50 less than Windows.