Google's PageRank algorithm works on the principle of citation analysis. Essentially, the search engine ranks the relevance of a particular website to your search according to the number of websites that link to it. This method results in more accurate, more relevant search results and is the foundation of Google's tremendous success. This means, however, that anyone who does research via a search engine (and, honestly, who doesn't?) will necessarily generate results which are influenced by the ranking system.
PageRank-style rankings favor commercial sites which pay other websites to advertise and link to them. So if you're looking for free information, there is a tendency that you will be frustrated by the top results. At the other end of the spectrum, the most authoritative sources of information on the web are often poorly linked or are not available for indexing by search engines. Academic output is usually of little interest outside of small groups. In the absence of commercial interest, authoritative information generally forms part of what is known as the Deep Web, which is the term used to refer to data which is not indexable by search engines. This means that the correct information you seek may appear very far down your list of search results, or may not appear at all.
If I can't trust Google, what about Wikipedia, you say? Wikipedia refers to itself as an "open-content, collaborative encyclopedia", meaning that "anyone with an Internet connection" may alter its content. Frequent users should take note that Wikipedia expressly states that it "cannot guarantee the validity of the information" and that there is no "formal peer review" and therefore no implied warranty of fitness "for any purpose or use whatsoever".
The point of all this is that, however noble the cause of free information may be in theory, money still makes the world wide web go round. Information is a resource, with significant extraction and processing costs: writing, editing, fact-checking, reviewing and so forth. Barring major changes in the structure of society, we can only continue to expect that free information is worth exactly what you pay for it.