If your feed is public, then it’s less like a party than standing at speaker’s corner in Hyde Park with a megaphone. And yeah, some of the folks in the crowd are corporate shills yelling ads back at you.
You're missing the point, that's not how 99% of normal people think it works, consciously or subconsciously, it's regardless of how it actually does.
People expect Facebook and Twitter to be local, and forget, because that's how human society works, but not computers.
Whether it's a couple of friends joking about defacing Marilyn Monroe's grave (with no real intention) or someone moaning about their internet, they don't expect to be watched by tens of thousands of corporations and hundreds of governments.
