Trust is one of those words that is complicated by personal feelings and situations. There is always the dictionary definition, then there is how the word is applied, used and understood for each situation.
When you pay for a six-pack of beer do you count your change or do you blindly trust the check-out person to give it back correctly? Is this a convenience store in a less than desirable neighborhood or a nice shopping center? Is the clerk wearing worn jeans and a t-shirt with some stupid saying or the store's uniform? The surroundings and the clerk's appearances automatically are assessed by our subconscious experiences and we react without even knowing it.
Do any of us here even trust each other? "Hi, my name is John Doe, I live at 123 Long Street in Casper, Wyoming and my phone number is 305-999-1234 and my wife is Jane Doe and we have a dog named Bingo." Of course not. Hell no. Any of us could be who-knows-who and do personal damage with that information. I do trust st-----h and de---, though. Sight unseen, just knowing about their intelligence and how they use it. Isn't that crazy, or what?
Before trust can be allowed, the hurdle of when meeting someone do they manage to cross that invisible barrier we all have of "is this someone I would care to have another word with"? Did they approach me or did I approach them? Each of us have our own definitions of that barrier.
So to answer the original question, there is no answer, except on a very personal level. This would make a good conversation subject while we all sit in a pub having a couple of beers, wouldn't it. We have an excellent brewery here in my hometown, how about meeting there this afternoon? Oh, and I lied, it isn't really Casper, Wyoming! You can fly into Missoula, Montana.