"You are either not giving us the budget we need to pull off anything useful, or you are giving us way too much budget and are dumb enough not to fear the consumer. In either case, we have pity on you. I should only have to utter the words 'Chevy Tahoe' and you should go running for the hills. We may say 'crowd sourcing,' but you should hear 'crowd slapping.' All crowd sourcing means is that instead of us coming up with ideas, you are going to put your brand in the hands of the great unwashed masses. Yes, advertising in not rocket science, but it is a scientific art of influence. Yes, everyone thinks that they can make a better commercial or campaign: 'Oh, oh, I know, you should have a commercial that (insert insanely lame pun here).' We do not walk into your company and tell your CFO to invest in gold. Why do you continually believe you have great ideas? If you did, you would be an ad agency, not a client.
If we are advising you to crowd source something, we are not worth the money you are paying us. Essentially, we have admitted we are out of ideas, and if you are saying we should do it, then you do not trust us to come up with ideas, and you have no idea how much damage the crowd can do to your brand."