Client receives my estimate, and then says, "I notice all these hours you've allotted for testing, requirements gathering, and meetings. I don't think we need these things. See, we want to do 'agile programming' which means we don't need any requirements! I'll do all the testing we need."
For an extremely complicated website with an estimated hundreds of active users, to be deployed in two months... sure, the technically illiterate client can be our sole tester! It's Agile Development, of course we can do it that way!