Hrm; these things work much better when I don't misread the actual question :)
Answering the question *asked*:
Depends on what I'm trusting them to do with it. Put it before their own? Absolutely none of them (I hope; see below on the topic of "enlightened self-interest"). Make decisions for me if I am incapacitated? Maybe two of them, quite likely only one (although, honestly, I trust neither of them to be completely able to get all of their "but I want what *I* want" reactions out of the way in order for that to be an *easy* decision process, especially once it boils down to things like, "Do we keep her on life support, or do we pull the plug?")
I trust my friends with my life every time I let one of them drive me somewhere, or let one of them cook for me, or mix me a drink. There are a few of them I trust to stab at me with plausibly-safe pointed weapons and armour. And there are others I trust to inflict different kinds of harm upon my person for other reasons. Those with intimate access to my person I trust not to bring life-threatening (or even just health-challenging) disease.
So I guess the short answer is, as it so often is, "It depends", and we'll be content with that.
How many do I think trust *me* with their lives:
Dear ghods, hopefully none of them, but in truth, probably far more than makes *me* feel comfortable. Being trusted is one thing, but having people trust *that much* is problematic in the realm of "enlightened self-interest", because if it came down to a "thee or me" decision point, I'm pretty sure there isn't a human being on the planet I wouldn't throw under a bus to save myself.
Trusting me with your life when my own isn't *also* at risk? Probably okay. I'm most likely going to do what I can to save you.
Trusting me generally to bail you out when it's not a life-threatening scenario? Now we're into the realm of context analysis, and odds are good if you're in a situation of your own dumb-ass choosing, I will provide enough help to drive home the lesson, then quite possibly leave you to figure it out for yourself, even if it means crawling out of a foxhole the hard way. I rarely have sufficient resources to manage my own problems, and I'm frequently all out of "silver bullet solutions" for anybody, so trusting that I'm going to be there for you all the time, or fix all your problems for you, isn't really going to do either of us any good.
I will swim out to you with a flotation device if you're drowning and pass it to you as safely as I can, but I sure as hell won't let anyone drag me down with them, not ever again.
So if you want to trust me with your life, that's entirely up to you. But if I don't explicitly consent to hold it as dear as or dearer than my own, then you may be making a very foolish choice of investments (and the expectations that go with them) that might someday result in a very profound disappointment on your part.
And there you have it.
http://www.marcandangel.com/2012/04/13/40-questions-everyone-is-afraid-to-ask/