It already has. Although it's not Facebook itself. It's the conscious effort of groups that could influence people. What makes facebook especially powerful is that it's designed to be addictive and interactive. People are too exposed to information and that drowning in data erases the boundaries between truth and lies. Especially when you have thousands of people piling on the posts. The inter-activeness makes the influence more powerful knowing that a certain opinion may appear to be the popular one.