It's a depressing thought, for even though most of us go through life aware that we're being monitored constantly, we don't appreciate quite how what we write online can be used against us. Employers, government agencies and fraudsters all trawl social media and forums for information on people they're targetting. People have lost their jobs because they were foolish enough to post photos of them enjoying a few days on the beach when they claimed to be at home with an illness. Many folk don't make it to interview, as their social media postings reveal their attitudes and leisure activities as being at odds with the ethics of the potential employer. Burglars use forums to find out when someone is away on holiday.
A good friend of mine was the victim of a fraud attempt a few years ago, with multiple mortgage applications made in her name. She was dumbfounded by how much they knew about her, realising that they'd found vital details from her FB posts, as well as a couple of forums that she used. Since then she's changed key details of her profile, as well as adopting different user names. She's a very direct and honest person, and dislikes the falsehoods that she has to remember to use simply to communicate with others.
I saw an interview with a man who'd worked for MI5, the British Intelligence Agency, who told of how he'd been tasked with a training exercise to ruin a citizen's life though the information he could find about him online. This wasn't some villain or spy they were investigating as being a threat, just an ordinary worker chosen as random. The trainee agent was appalled, for though innocent passers-by are used for exercises such as trailing them through a crowd or testing facial recognition software, he effectively ruined this stranger's life by tampering with his bank accounts and health records. Such government interference formed the plot of Will Smith's best film Enemy of the State—
truth is always stranger and nastier than fiction.
As the tagline for the movie goes: 'It's not paranoia if they're really after you.'