[wpietri]

As a frequent introducer, I would never forward the whole chain.

Consider the case of a friend looking for a job. If they come to me asking for an introduction, they may be open with me about things they wouldn't tell a stranger in the first minute of contact. E.g., concerns about the target company, fears they might not measure up, things going on in their life. It's hard for me to know what they don't want shared, I want to minimize the risk a violation of trust, and I don't want to guess at what the recipient might have an issue with. So I'll always write my own intro or ask for something I can forward.

Also, if someone dumps some unwelcome request from a pal in my lap, I'd be irritated that I had to do the work of bowing out. It's their friend, not mine, so it shouldn't be my problem. For that reason, I always ask permission to do an intro unless I have strong reason to believe the intro would be welcome. (E.g., if somebody told me they're looking for developers, I'll do intros without confirming an interest in each specific person.)

[danielweber]

I once worked at a place where the board members were having a discussion about the CEO, and then of the board members decided to just cc: said CEO into the conversation at random, because "well we are talking about him and he deserves to know."

That board was not well-functioning.