The reason for using cloak technology is twofold. First, because viewers never see the page that is presented to the spider, the code can not be stolen. In highly competitive markets the ability to conceal code from the prying eyes of competition can be an extremely powerful advantage. As a result it can be optimized to it's fullest potential. Think about that for a second.
Nobody sees the page except for the spider.
That gives cloaked pages an extremely competitive advantage over web pages that were optimized to accommodate a professionally appealing design. That said, there are two methods of delivering cloaked pages - Agent Name Delivery and IP Address Delivery. Likewise, all spiders have a name. With this knowledge, delivering a specific page based on agent name is a rather simple task. While very effective, agent delivery is not a foolproof way to protect your code.