There are other sources for maps data, and many people have 3d modeling software.
So I'm not sure how this is "so much power" concentrated in one organization.
I've worked with aerial surveillance systems, the types used on police choppers. Put the crosshairs of the flir camera on a house and it will tell you all kinds of stuff: age/race of occupants, arrest records, warrants, tax status, etc. Amazing for LE, but a bit big-brotherly for my taste.
In the wrong hands, in the wrong circumstances, data fusion has incredible potential for abuse. IMHO. :-)
You can blackmail me if you know something no one else does. You can't if you know something everyone else does.
Services like this fix asymmetric access to information. They're not revealing anything new.
I believe the potential for abuse exists. Everything is fine now (here in California). But when the next crisis comes, data-fusion can be a powerful tool for authoritarians to control their opponents and suppress dissent.
If you're a normal citizen who has technical skills, yes, you can do exactly the same data extrapolation with publicly available datasources.