[Frumanchu]

The implication was that "want to bet?" was short for "Do you want to bet?" which makes more sense than "Do you want a bet?"

Anyone else want to weigh in? Anything to avoid the CvE debate... :D

[beckett]

Dawkins definitely got the idiom wrong. It is not "want a bet" but "do you want to bet," abbreviated in slang as "wanna bet."

A bet cannot be given away, as the question "want a bet?" implies. Betting is a collusive act, and the preposition "to" must precede the infinitive verb "bet" for the phrase to have meaning.