I'd never ask someone else, even if it's a close friend, to borrow his carbon bike, regardless of how much it's worth. Not that I don't trust myself to take care of it, because I'd take more caution with it than my own bike, but just don't want to put him in an awkward and uncomfortable position. So, I wouldn't lend it out, and I hope that a close friend wouldn't put me in that same awkward position.
A colleague or acquaintance? Hells, no!