Facebook's immense power makes it much more difficult for competing messaging systems, social networks, VR-related companies, and others to enter the market. When they do find any success, Facebook usually acquires them. The effects of monopolies and oligopolies on economies and societies are well-established.

If you live in the US, or Europe, or pretty much any country Facebook operates in, the company is spending millions of dollars every year to lobby your government. While that may not sound like a lot, political influence is surprisingly cheap, and effects you whether or not you choose to participate in the political process. The CEO meets regularly with the president of the United States and his close associates, and has met and spoken with many other world leaders.

Facebook is a major facilitator of violence and ethnic cleansing around the world (https://time.com/5197039/un-facebook-myanmar-rohingya-violen..., https://www.reuters.com/article/us-facebook-india-content/fa..., https://www.buzzfeednews.com/article/ryanmac/chinse-media-fa...). You might argue that if they couldn't use Facebook, people would just use some other platform or tool to accomplish the same goal. That's possible, but if it's happening on Facebook, the company has a responsibility to take action, and they have failed. I don't think there is any other platform that could be used as effectively as Facebook and WhatsApp for this purpose.

Even if you don't use Facebook, they likely have a profile for you if anybody you know uses it. They collect contacts from peoples' phones, and scan for faces in all photographs (and correlate the results with other photos). If you don't have robust ad and tracker blocking in your web browser, Facebook is tracking your behavior with their ubiquitous like buttons and analytics scripts.