The problem with your argument is people choose to give their information to Google/MS et al.
With the government / NSA / GSCB. You firstly have / had no knowledge if you are handing over the information and secondly there is no way you can choose not to use the GCSB/NSA.
So to compare a private company you have chosen to use vs a government collecting all the metadata beggars belief IMHO.
I'm not sure people to choose to give their information to Google/MS as you suggest. In many cases they don't even know it's happening.
On a very superficial level just look at what ads get served up on your browser when you do a Google search or for that matter what results you get from a Google search. They're based on your previous browsing history. The same Google search done on separate computers most often throws up different results purely due to the differing browsing tastes of each computer owner. What other intelligence is the likes of Google collecting?
Then there's the in App stuff on mobile devices that goes on unnoticed in the background often without your permission or knowledge where various apps track your movements etc.
At least with the government et al we all know they have been gathering intelligence for ever, why should that be any different know. I see no surprises there.
One thing that I haven't seen being discussed is the fact there is a massive mountain of data involved and it must take a massive amount of resource to analyse this data. Do they have the resources to look at it all? I suspect they don't. Therefore they will be only looking for high profile stuff. Anything else will slide under the radar.