What is the exclusionary rule?

Hypo 1: Police suspect Bob is counterfeiting baseball cards, selling them on eBay, and transporting them through the postal system. Rather than get a warrant to search Bob's house, Police talk to Bob's neighbor who points out that Bob is never home at 4:00 pm and he keeps a hidden key under a fake rock. Police take the hint, find the key, and enter Bob's house where they find a pile of counterfeit baseball cards, envelopes, stamps, and a computer open to a website entitled, "How to Defraud People on eBay by Mailing Counterfeit Baseball Cards." Result: All of this evidence would have been incredibly useful in prosecuting Bob, had the police gotten a warrant. By not getting a warrant, their search of Bob's home violated Bob's 4th Amendment rights and, thus, are barred under the exclusionary rule.

Hypo 2: Same facts as Hypo 1:, except instead of the police entering Bob's house, his neighbor decides to break in after the police speak to him. After the neighbor breaks in, he photographs all the evidence and sends it to police. Result: The exclusionary rule doesn't apply here. Why? Because The Constitution protects people from abuses by the government. In other words, because Bob's neighbor is not an agent of the government, their actions—though wrong—do not prevent the government from making use of the evidence discovered. We'll cover this more in other cards.