Who runs the pages of companies on twitter and facebook?

It dependent from company. Almost all companies use internal team of SMM experts (Social Media Marketing) that run pages and coordinate efforts with marketing team.

There is cases when external companies (SMM agencies) run company accounts under agreement.

To run the pages of companies on twitter and Facebook, company may use the internal social media marketing expert or they may hire social media marketer from outsides.

simply,to run the pages effectively on any social net working site such as twitter, Facebook a company need expert social media marketer.

Social media marketers run those pages and you can find a jon on many job boards by searching social media community managers

My theory is so it can't be bossed around by the United States of America and the United Nations. Lots of Chinese do have rights and it is a nation of advancement and backwardness. China is a sort of oxymoron. China is very sophisticated in urban areas and very backward in rural areas. Though that will change soon. Our government does Research and Development partnerships with them. And our nation has the only free trade agreement with China. Chinese have many billionaires and many more being made yearly. Chinese like NZ and vice versa. Lots of Chinese come here as tourists and to study. Chinese recently let their state TV station buy a NZ made kids TV programme.