Zig Zagged: It looks like Alice convinced Bob the loner to join thanks to trust! Except he just wanted to betray Alice to prove no one can be trusted. But she explains she knew he'd pull a stunt like that, and still trusts him, which makes him reform!
No one trusts anyone else, so the occasion does not arise.
No one expects trust to change anyone's behavior, and it doesn't.
Lampshaded: "So he switched sides because you trusted he would switch sides? Any chance you could trust me to win the lottery?"
Invoked: Alice realizes Bob may fail, so she purposely gives him pep talks about her trusting him to give him confidence and resolve.
Defied: Evil Overlord Charlie knows Alice can make his mooksswitch sides if she gets a chance to make an "I trust you" exchange, so he uses robot mooks.
Discussed: "No, Alice, trusting Bob to defect just because you trust he'll do the right thing doesn't mean he will."
Conversed: "Wouldn't it be awesome if you could empower or change people by trusting them?" "No, it'd be too much like mind controlling them."
Alice feels a need to have faith in others because she has none in herself. She's thus unable to do much of anything on her own, and even minor betrayals of her trust cause her to collapse emotionally.
Trust is horrifically fragile; all it takes is one betrayal and a person becomes jaded and paranoid of others.
Reconstructed: Despite the bitter sting of past betrayals, Alice refuses to give up on trusting others, instead learning to be a little more cautious and a lot more observant.