And ... I'll pessimistically assume that forgetting one of those accounts is grounds for federal prosecution.

I've had dozens of reddit accounts over time. Some just for funny names, some for anonymity. Literally do not remember all of them. I have multiple accounts on platforms. Some for looking at porn and not conflating that with charitable work I do (and negatively impacting the charity) and some just to not be associated with being a lil'freak to my family. Again, I can't remember some accounts, websites etc. over time.

I couldn't list all my historical social media accounts if I tried. Maybe my use case is different to many people? But ... shrug looks like it's politically unsafe for me to come to the USA?

Just another reason not to travel to the US.

So I guess the NSA did scoop every post of every platform in order to track down bad people. Surely a worthy effort on their part!