There is a debate going on, both within our institutions and in the research community. Is Google a tool or a resource? I feel that Google is just a tool, an excellent one that allows us to access a universe of information. Unfortunately, the quality of the information is always in doubt. Information from a fake website or a misleading post could be included in the search results, maybe even at the top of the list. The same reasons you don't rely on Wikipedia apply even more to Google. Google has never laid claim to delivering only quality, vetted information. In fact, they have taken great pains to do the opposite. Look at the disclaimer at the bottom of the page here and listen to the conversation Richard Leiter and Company had with Google Scholar's Chief Engineer here.
As a researcher, I know the importance of confirming anything I find on Google and noting if the information is suspect and cannot be verified. In CI as in law, it is important to have a high degree of confidence in the information that your analysis and recommendations are based on. Google alone does not instill that confidence.
There is a reason we pay for services like Lexis Advance and WestlawNext. These services ensure that their subscribers have access to current and vetted content, often with editorial review. I'm not saying Google isn't useful. I am on Google several hours each day. However, it is for these reasons I don't conduct legal research on Google when I have these services and others like them at my fingertips. Just like any tool, a thorough understanding of its limitations is necessary to get the most out of it.