Saw this article about Shanghainese to brush up on their Mandarin and then seeing this article about TV hosts not to use HK or Taiwanese accents when speaking Mandarin. Interestingly enough...
Only just over half China's 1.3 billion people can communicate in Mandarin, the official Xinhua news agency cited a national survey as showing last year, while almost 90 percent can speak dialects ranging from Cantonese to Hokkien and Hakka.