Excuse #1 - Google, Apple..etc are doing it too. This is what 5 year old children say when they get caught doing something they know they shouldn't while their brother (Google) or sister (Apple) does not (this time). If you don't understand why this is a completely nonsensical position try following defense in court.. "yes your honor ... I was drinking and driving but everyone else I was with did it too so its ok."... Go ahead...see what happens.
Excuse #2 - ALL of your data is necessary to provide a feature. Examples like Siri, Cortana, Google voice are often paraded around. They need to rummage through your address book to know who "Frankenstein" is before they can call ... Need to know what's in your calendar and where you are at...right? Well no... your "Intelligent Agent" needs to know. There isn't any reason said agent can't execute locally and provide the same services if user prefers not to upload a list of all of their acquaintances and agendas to Microsoft. These systems are architected the way they are because spying is profitable not because they maximize value to end users. Your phone can know your at the florist without sending your location to Microsoft. Your phone can remind you to pick up flowers when you call someone. It isn't impractical or unrealistic to implement. It just isn't profitable.
Excuse #3 - Browser information leaks... Chrome, Firefox, IE keep thinking up new excuses with mostly negative to users to get a piece of everything you are doing with every revision. Some of this shit is offensive blatant one finger salute ...Sending your searches to bing even when you don't use bing.... Uploading your browsing history to Microsoft...there is no rational excuse for this and I can't believe anything approaching a majority of people want this to happen by "default" for any reason.
Excuse #4 - You can turn it off - Coupled with intentional UX design blurring demarcation between local and internet promoting accidental leakage and turns the leakage spigot to 11 by default knowing most users won't know, care or understand enough to change settings which increasingly are ultimatums or don't actually stop data leakage they purport to stop. Now the pot is really starting to heat up... Now Microsoft is retroactively saying fuck you people we will collect shit and there is nothing you can do about it. That they have the gall to say this to their *customers* I personally find amazing.
"Finally, we will access, disclose and preserve personal data, including your content (such as the content of your emails, other private communications or files in private folders), when we have a good faith belief that doing so is necessary."