Pay-per-click advertising is not without its problems-especially "click fraud", the practice of generating bogus clicks for devious reasons, such as making arival advertiser pay for nothing.
Customers who sign up for a bundle of services and its associated discount cannot defect to arival provider of any one of the services without losing the discount.
消费者只要认购了打折后的捆绑式服务,就不会去选择竞争对手的任何单一的无折扣服务。
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Yet Brown believes Quora could still reshape the Web without becoming a blockbuster to rival Yahoo Answers.