As with anything, it always depends on the context. If I'm introducing someone to an investor I barely know, I'll make sure they opt in. If I'm introducing them

As with anything, it always depends on the context. If I'm introducing someone to an investor I barely know, I'll make sure they opt in. If I'm introducing them to an investor I see every day and know they trust me, I'll just go for it w/o the opt-in. This article and Fred Wilson's are great examples of how to maximize etiquette.