It's nitpicky, but you're using the word trust wrong here. I don't have to completely trust the people who signed your key, and I don't have to trust you at all. I have to trust the people that signed your key to have done the proper background checking. That's all. I could think your a vile, lying, cheater, but still know that when you send me that lying email, it is indeed you sending it.

In the aggregate, you don't even need that much trust in any individual, just a spam filter on the trust endorsements.

Yes, you're correct, thanks for enlightening me.