US advertising agency and media executives have shunned the event, which is being held only 200 miles from where Israeli tanks have been in action.
Organisers had considered switching the congress to Dubai had the Middle East violence spread. But they say the event will now go ahead as planned.
Sherwood said: "I wanted to go but the agency's insurance company won't cover me. Beirut, with its history of trouble, seems an odd place for the congress and it's very close to the danger zone. I don't understand why it hasn't been switched to Dubai."
Wally O'Brien, the US-born director-general of the IAA, commented: "Our original target was for between 980 and 1,000 delegates but we're not disappointed with the numbers. Many other conference organisers would have been happy with two-thirds of that figure."
Privately, IAA executives acknowledge that the Beirut event was never going to be as popular as the London congress, partly because of its preoccupation with marketing communications issues in the Middle East.
"Americans have knocked the event off their list partly because of the economic situation which has led to fewer people doing more work," O'Brien added. "But there's also still a lot of fear about travelling."
Scheduled speakers also include James Best, the BMP DDB group chairman.
He said: "I don't feel threatened and as long as the situation doesn't deteriorate between now and then I'll be there."