In the UK, radio adverts can be banned for being too quick.
(Recently a radio ad by Vodaphone was banned, because the legal terms were read out too quickly. In fact the actress recited a 30 word legal 'terms and conditions apply' disclaimer in just under 8 seconds. You can listen to it here, then try it yourself. Here's the text:-
"Subject to status, availability and connection to 18-month contract. Unlimited calls to landlines or Vodafone Mobiles only. Fair-use policy, terms and 60-minute call cap applies".)