Someone burned by one in whom they have trusted will, of course, grant those incremental "trust points" with less generosity than one who has never been in a position of having their trust misplaced.
Trust is the single most valuable commodity I possess, and is not bestowed lightly. There exists no 'right' to my trust, it is a gift that I may share with others. It is something to be earned, rather than expected.
Unfortunately there are many people in the world who treat 'trust' as commonplace, who take it for granted, or dismiss it's value out of hand *sigh* That sort of behavior is what leads to the less generosity that Sandra mentioned.
'Give people your trust until they break it' Why? Turning the equation around is equally valid. Perhaps more so, really.
Trust also has to do with protection. In the end I am the one who has to protect myself 'cause no one else is going to do it.
...who knows that pretty words are nothing more than that...