Is there evidence that the data is being used to prosecute/harass/intimidate people?

So you're okay with the TLAs snooping around and watching what you do provided they don't act on it? I'm not, if only as a matter of principle. To quote the great movie Anon, it's not that I have something to hide, it's that I have nothing I want them to see.

Besides, remember, this is the United States: just say terrorism or national security, and due process and habeas corpus go out the window - in which case, you may not hear about somebody being harassed or prosecuted at all.