He said another problem was sneaky users "can get all their mates to connect and give the result they want.
"It's not an easy thing to do and get right. It's live TV. You don't get a second chance to get it right, and accuracy is critical."
TV3 has exclusive rights to use the worm. TVNZ corporate affairs spokeswoman Georgie Hills said TV One did not plan to use a worm-like device in any of its party leaders' debates.
Worm or no worm, networks and politicians may need creative ways to convince undecided voters like Amy Yalland.
Yalland, 22, a graphic designer, split her vote in the last election and said the last TV leaders' debate she saw was forgettable.
"I remember thinking John Key seemed a bit hopeless but not much else stands out."
She welcomed Tarrant's views on making politics more entertaining but warned against trivialising debate.
Office manager Gabby Newton, 31, was also an undecided voter and said she had no interest in watching the debates.
"I might read up on it in the Herald," she said. Newton said she was a fan of Key but didn't actually follow any party policies.
Veteran campaigner and retiring Wigram MP Jim Anderton said the worm could lure desperate politicians to say "humiliating" things.
He said politicians were disgusted when Peter Dunne repeatedly used the term "common sense" during a 2002 debate.
"The average senior politician wouldn't dream of using such a banal term. Most of us would have been too humiliated to use it. It was very manipulative."
Anderton suspected some leaders were receiving training on how to stimulate the worm, as they did in previous elections.
Peter Dunne said Anderton was "deluded". "I think that's ridiculous. I use the term frequently, worm device or no worm device."
Dunne said he received advice from strategists before the 2002 worm debate, much of which he ignored. "I think the worm is a huge distraction, even though I've been a beneficiary of it on a few occasions."
TV3 plans to roll out the worm for a Key and Phil Goff debate on November 21, in the week before the November 26 election. TV One will hold three debates. One will involve minor parties' leaders. The others will be between Key and Goff.