It's radio. Anybody in the vicinity can listen in all they like. Back in the bad old days this was Industry Canada's position, that cellphones were not private and there was nothing anybody could do about it.
Unlike AMPS, the communications are digital. So what. If you are sufficiently determined you can decode the data you have captured.
If push came to shove I'd set up dummy Facebook and Twitter accounts and let CBP see them. No good way to tell which of the several hundred Laura Hallidays on Facebook is me. Post some pictures of cats, a few likes, done.
I already engage in some self-censorship. There are a few CDs (mainly Russian and Israeli acts) I leave at home when I cross the border.
I accept that advertising is what supports platforms like Facebook (indeed, just about everything on the internet), but please remember the user in all of this. My computer is mine. My browser is mine. Monopolizing it while you play an irrelevant auto-play video is just not cool.
Facebook is relatively tame in this respect. I've seen worse.
I remember a few years ago seeing that my Amex was about to expire, and wondering when my new card was going to arrive.
Then I got a phone call from American Express. Had my new card arrived? No. Did I live alone? Yes. Did I know any men with Russian accents? Uh, no...
Yup: somebody had stolen my card and had gone on a shopping spree with it, triggering security alerts. My bill that month was about 50 pages, interesting charges (all local, curiously), then pages of Credit for Fraudulent Charge. I asked what my liability in the matter was and they said zero: unlike most other credit cards, American Express cards may only be used by the cardholder ("non-transferrable"), and if the merchants hadn't verified the identity of somebody who was really unlikely to be named "Laura", that was their problem, not mine.
A long time ago I was working with GPS applications and their internal representation of longitude meant our Null Island was in the middle of the Pacific Ocean, 0 north, 180 west.
We figured out the conventions of the mapping application we were using (no Google Maps yet, and the documentation was vague) by trial and error. Our first attempts to plot GPS fixes from a drive along a local freeway showed a blank area with no freeway, nor much of anything else. We found that we were drawing a map centred on 49 degrees north (correct) but 123 degrees east, out in the middle of nowhere near the border between China, Mongolia and Russia. Nearest town Harbin, China...
Step 1: Apple introduced the iPad and everybody was desperate to get one because it was the trendy item to have.
Step 2: people started figuring out what they could do with a handy portable computer.
Step 3: everybody who had a use for a tablet had one and the sales dropped off to replacement level.
Any remotely interesting new product is going to grow at unsustainable levels until the market is saturated. Then the growth stops.
If you want to use less air conditioning, don't live in Dallas. Or Phoenix. Or Las Vegas.
Doubt is not a pleasant condition, but certainty is absurd. - Voltaire