Alexa

All of the consumer websites and social media websites listed in the top ten of  Alexa’s Top 500 websites are Web 2.0 sites.  YouTube.com, Facebook.com, Wikipedia.org, Reddit.com, Qq.com and Taobao.com are all Web 2.0 sites. I think the factors that contributed to their popularity are the same features, functions and factors that make them Web 2.0 sites.