Hm, I wouldn't be so sure about that. Scandinavian countries seem to have their stuff together much better than we do. There are some downsides, but overall quality of life for citizens is much higher.
This is kind of a fine line. In the case of data mining, it's not so much people choosing what they're sharing as it is companies going through and compiling records based on even actions that would casually be considered to be fairly private, like what someone is buying at the grocery store. It seems a little wrong that anyone other than my credit card company or bank should be sharing my every purchase with, say, my insurance company.
While it's certainly true that the 4th amendment is above congressional law, someone has to step up and challenge it for it to be overruled by the SCOTUS. The SCOTUS also have to agree that it's a case they want to take on. It's not so simple as someone pointing out that "Oh, you can't do that. Lulz!" Basically, just because a law may be unconstitutional doesn't mean that it'll be overruled right off. And given that our current SCOTUS tends to be fairly happy with giving the government more power (and isn't exactly up to speed on how technology works), I am not so certain we'd manage to get a majority against this. We'd probably get Sotomayor, Breyer, and Ginsburg, but the rest are fairly iffy...
So, hey, can we maybe start thinking about shifting the burden of proof back to the person making claims? Seems like that's the way to go. I can accuse anyone I want of anything - it's not the world's job to tell me why I'm wrong, it's MY job to say why I'm RIGHT.
I actually disagree - sites like Facebook and G+ aren't as focused on "issues" per se as a site like reddit is. Reddit is somewhat interesting in the way its bits and pieces are set up and devoted to each their own little niche, so it's much easier for like-minded people to migrate into the right places. Facebook, however, is based on real-life social interactions for the most part. Proximity, rather than belief, is what influences who gets together there. For apps like the ones you describe to be used, there first must be a bunch of people WANTING to use them. Reddit gets people excited, and makes them want to use them. Facebook is concerned with the local social scene because that's where its user base is drawn from. Reddit is from *everywhere.*