Web Search, "Deep Web," and OAI Protocol (Muddiest Points)

I was reading that Google licenses a database to Yahoo! [http://google.yahoo.com]. The internet post also said that the licensed database supplied content which Yahoo! did not have in its own database. Is this accurate?


It seems like many search engine companies such as Google are trying to implement technology to crawl the “Deep Web” but what are the dangers of doing so? Certain websites were saying that many hackers and other people engaging in all sorts of shady activities reside on the “Deep Web.” Besides accessing information what are the known dangers of perusing the “Deep Web”?