We're living in a scam economy... My best policy is to not really extend trust as much as extending "tiered courtesy" and carefully observing the results to determine how much more to give... I primarily work hardest on my own trustworthiness, because I know very well how easily any of us can become corrupted by bad times.
Even some of the strongest marriages and families are being torn apart right now because of broken trust.. In my experience, trust is never a permanent state, although I wish it could be. One thing's for certain, there's not a single corporation I trust right now at all, they've been pretty merciless towards everyone except for their Investors and vested leadership.
At least in the USA, one small mistake in trust or lack of safety in certain things ("something happening") could cause you to be on the street within months, even for people like those here on HN who generally have good jobs and such. I think it's getting a bit primal due to that here. We're acting like animals because we've been treated as such for decades and generations and we're finally sick of it. That's my opinion, not really backed up by anything.
I think people have been bitten in the back enough time by assuming the best that people have switched to thinking this way. When you try to be nice and keep getting taken advantage of then it's hard to stay nice.