How is social media being used to create a more open government and facilitate policy discussions?

Politicians and political organizations are taking advantage of social networking sites to promulgate their cause. How?
By using the services of Facebook, Twitter and other websites through advertising and by persuading online groups and users to join their cause.

These pages are designed to accommodate users from around the globe and it enables them to participate in discussions.
In a lot of cases, Public relations officers or the government official is running and personally answering the questions and actively participating in the conversations.
A certain feature of mediums like these is that the person running the page is able to delete the comments or ban the user from posting or even visiting the page.