I was once engaged in a discussion on Facebook about Obama's foreign policy. Around that time, I was going to apply for a US visa. I stopped the discussion early. Semi-consciously, I was worried that what I was writing would be checked by US visa officials and would lead to my visa being denied.

Not necessarily an entirely trivial fear: while discussions about foreign policy probably won't get anyone's visa denied, "officials Googling a person and then denying them entry to the US due to something trivial" has happened before.