I understand your concern about corporations breaching your 4th amendment rights, but your reasoning is misplaced. In fact, this case is a great example of the 4th amendment being followed, not circumvented.
The 4th amendment does not guarantee protection against search and seizure; it limits when and how searches and seizures can be exercised. Here's a portion of the 4th amendment for you: "...no Warrants shall [be] issue[d], but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.” In this case, Google's tip was not used as evidence to convict this man of a crime. Google's tip was used by police to justify probable cause that a crime had been committed. (This does not mean he's guilty of the crime, only that there's a greater likelihood that he committed it than he didn't.) The police used this information to obtain a search warrant. I'm sure that the evidence they used to convict him was gathered through the exercise of that warrant.
Google's tip is no different than a tip coming from any other source. Say a bank teller (for association's sake, let's say the bank was incorporated) was just depositing some money for a customer who drove up to her window, and she saw in her security camera what she believed to be a missing child. She calls police and reports what she saw. The police go to the bank and look at the recorded camera footage and agree that the image captured does resemble a missing child. They grab the license plate number from the footage, trace the registration to its owner, obtain a search warrant, go to the owner's residence, search the premise, find the child, confirm it's the missing child, and convict the individual of kidnapping (and probably a host of other charges to boot). In this circumstance, private information (whether an e-mail sitting on Google-owned servers or a bank's CCTV DVR) shared with police is used to meet probable cause and obtain a warrant. And in both circumstances, a search and seizure is warranted.
If you want to minimize your risk of a warrant being issued against you, don't display evidence of a crime outside of your own home. (And when the police come knocking on your door and politely ask you, "May we come in?", unless they flash a warrant in your face, don't be polite back.) And while IANAL, for more information about the 4th amendment and warrants as written by one, I strongly recommend you read The Illustrated Guide to Law. Very, very informative.