To learn about a new company or product, the only person I really want to talk to is the CEO. It may just be me, but I like to focus on just one person during a pitch. So if the CEO is at the meeting, the presence of the COO, and the VP of something-or-other, and the PR flack too is simply distracting. One chaperone should be enough.
See also, Tip #32, Hush, Now.