But there are different kinds of trust. Sometimes we trust out of necessity. This is the kind of trust I have for my doctor; I trust that he can set my arm correctly after I break it, or diagnose a condition. Sometimes we trust out of respect and love. This is how families trust each other, and is the trust behind "blood is thicker than water". And sometimes we trust by alignment. This is the trust between colleagues.
Trust by alignment is about respect, but more importantly it's about shared values. For example, I work with Matt Heusser fairly frequently. When Matt emails me and says, "Here's something we should do. Are you in?", I almost always say yes. I don't ask too many questions; I just trust that it will work out. Why? Because Matt and I share many values. He's as careful with his reputation as I am with mine, so if he thinks this will enhance - or at least not harm - his reputation, then I can feel safe it won't hurt mine. Matt and I also share the idea that engineering advances when thinking people put aside the egos and grandiose pronouncements in favor of sharing experiences and ideas. So if he says, "let's do an article together", then we're going to wind up with an article that I can be proud of, because I know that he's not going to put in content that I completely disagree with. We have alignment of professional values, and that means we can trust each other.
So ask yourself whether you can trust someone, sure. And recognize that trust comes in many forms. Trusting by alignment, or necessity, is perfectly acceptable. Know that you trust and know why you trust. That will tell you when to trust.