what are your favourite features of Social Media Platforms like facebook?

I know that there are many really exciting and fun things to do in social media like games and apps and competitions and even the less considered items such as the like buttons and sharing facilities so i would like to know what exaclty are people doing on facebook and similar sites. what other sharing platforms do you use and what are the features that make them stand out? Yahoo answers does count so you can talk about this one if you want

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