Regarding the specific point originally brought up in the original post.
2) Cortana. In other words it does EXACTLY the same thing that any other predictive system does. Siri? Does exactly the same thing. Doesn't even have to be voice. Google does the same thing for Instant Search by default. If you don't like it, turn it off. It's not hard.
3) Data Syncing. Again, EXACTLY the same thing their competition has been doing for some time now.
4) Targeted Ads. Again, this is old news. Everybody is doing it.
If your privacy is that important to you, you shouldn't be on the internet. It's that simple. Privacy vs Convenience had a war and privacy lost some time ago. Do these companies have "evil" reasons for doing this? Sure. Most corporations are driven by greed. If they can make more money off you, they are going to. However, these waves of anti-Windows 10 posts are ignoring the amount of features that NEED this level of invasive mining to work. Features that the majority of Joe Public wants. Therefore you can expect things to keep heading that direction.
For those of you riding the Microsoft is evil train, let me ask you this. How much is your privacy worth to you? Actually think about that, rather than just give the knee jerk reaction that my information is my own. While in principal I agree with that statement, there's more to it than that. Here's what I mean by that.
Facebook, for example, does nothing of worth to me. Therefore I have no incentive to sign up for an account and give them access to my data. Pretty straight forward. We can put a little check mark in that privacy box.
Cortana/Siri. Things start getting a little grayer here. If I'm on vacation, I like being able to pull out my mobile device and ask it to find a restaurant and be greeted with results in the right physical area rather than find somewhere to park, pull over, and do a manual search for locations in whatever city I'm in which are going to be somewhat inaccurate anyways. That requires access to my location at a minimum. In order for that system to work well, it needs an ever expanding sample of both raw data and voice sample's itself. Is having my phone's OS know where I am worth that added convenience? I'm willing to bet that for the vast majority of people, the answer to that is yes.
Data Syncing. Again, this isn't so cut and dry for the majority of people. If you're the type that takes a lot of pictures or video with your phone, having it automatically backed up is a feature most people would like. On a PC, many people pay for software to do that for them. Remember, iCloud got hacked. How many people do you think stopped using it after that? I'll bet it was almost nobody. At least not after the first time they lost an ever so important selfie or picture of their cat. Ditto for the more personal information like contacts. Most people LOVE having their contacts automatically synced across multiple devices. Tell people they can buy a new phone and it will automatically have all their contacts on it? Most people will love it. Regarding specifically the Bitlocker aspect, that's along the same lines as the WiFi sense argument that was made in a different thread. OK, IF OneDrive is hacked, somebody will have access to your Bitlocker key. OK, now what? They don't have the computer the key belongs to, so what exactly is this doing for them? So, is having Microsoft have access to my data worth it in exchange for free automatic backups? Again, for the vast majority, the answer is going to be yes.
The only way you're going to have true data privacy is if you unplug and live in a box. We live in a day where nearly everything is available in "Smart" form. Things like home automation rely on having access to information like your location and schedule to work. Most people see this thing as "the future".
I'd also put money on most of you not being nearly as secure as you think you are.
I've upgraded 4 computers at the house to 10 and don't regret it in the slightest.