WPP Group CEO Martin Sorrell doesn't sound happy about some of the world's biggest advertisers' decision to regularly delay paying agencies weeks longer than before. "I don't think our purpose is about banking -- we're not about a bank -- or extended payment terms or agreeing to supply payment terms in low-interest conditions," he told Ad Age in this interview during the Cannes Lions International Festival of Creativity.

Agencies that accept the marketers' terms, though, could force others to follow suit. "You're only as weak or as strong as your weakest link," Mr. Sorrell said. "And if there are people out there who are prepared to take those risks, then obviously it will compromise the whole industry."

Watch the video for more from Mr. Sorrell on that subject as well as creativity and the foolishness of a rival's alleged guaranteed ad spending with Twitter.

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