Trust is complicated, comes in levels or degrees, what type of trust or situation has than other element of factors involved. There is an unknown factor in trust. We can't predict the future or what might happen - which brings faith into the scenario in large extent. We can base trust on honesty, integrity, past behavior, morality, legality, or then again you can base it solely on actions of the present and proven track record starting from that day forward. Someone young might be just as trust worthy as someone old. The degree of trust varies from if it's just a daily interaction of friendships, to casual play, to scenes or a full time relationship.

I for example know some that push scenes to safeword almost every time, yet this is something I don't agree with doing as a 'rule of safeword' and would not trust mine in a situation like that or advise it.

Someone's past behavior or 'earned credit rating' as stated in last post, can be very important factor, but not necessarily the overall last word to establishing trust. Using that same example, that would be like saying just because you paid late a few times, or had one default loan, your going to do that the rest of your life.

I think on matter what is used as establishing trust, or for what particular situation and amount of trust, you have to always remember that a certain amount of faith or 'gut instinct' is integral aspect. What someone might do in a unexpected situation that was unknown or seen coming, might mean more then all the above.