Gossip, anonymous comments, Yelp! reviews. These can all be valid, irreplaceable sources for research. However, it's important that the sources you select match both your research goals and your class assignment requirements.
For instance, if you want to understand how people feel about a political topic, first-person narratives will be invaluable. In such cases, primary sources (first-person testimony, receipts, official documents, diaries, online comments, etc.) are appropriate. Primary sources are critical to in-depth research and answering very specific research questions.
If you want to get a general sense of how a group of people communicate, secondary sources are needed. Secondary sources provide analysis, comparison, background information, and/or interpretation (academic journal articles, encyclopedia entries, etc.) and are appropriate for general research and answering broader research questions. Secondary sources often synthesize (combine) many individual perspectives into a more generalized perspective.
In a class like this one, primary sources can be useful additional or anecdotal evidence.
For general help with detecting 'fake news,' see our library guide on Research.