Additionally, some sites are primarily built for other purposes but have a social media component as well, such as the Amazon online store that has user reviews and customer questions & answers, or news sites that have comment sections.
I didn't know that Amazon can also be considered social media:) It's actually interesting to know that a website/app only needs some features of a social platform to be categorized as social media. Given this, what are the preliminary factors that determine whether a web/app is social media or not since it's kind of vague when we decide which is and which is not?