I think there are different levels of trust and those levels may change as our experience with those people evolve and change. As far as business goes you try to make the best decisions you can but risk is always a factor.
Of course when you have done business successfully with someone over and over the level of trust increases. One of the best snakes in my collection I recieved sight unseen because I have done so many deals with the person when he said it's a smoker and i trusted him. That took 9 or 10 sucessful transactions for me to feel that way.
I never give unescessary trust to anyone. You never know who is going through a difficult time (drugs, gambling, debt) and dangling a carrot in front of them can be too tempting. Even friends

. For example if you are throwing a party don't leave cash, valubles and jewerly lying around, it's not responsible and you are asking for trouble. i have heard the "It was only people I knew" line.
I strongly believe in vibes, impressions or instincts and I like to look someone right in the eye when I ask an important question. Eye contact and body language tell alot. Online we don't get that so referrals and reps are huge.
I do take risks sometimes but ONLY if I can afford to loose if it doesn't work out. In other words don't take risks with the rent or food $ for example.
Trust has many levels to me, it all depends who and what is at stake.