With launch of Google+ and Google+ Brand Pages, here comes a great change to another social networking giant “Twitter”. Though we have not heard anything from the horse’s mouth yet, but there are evidences which says Twitter has removed the restriction of DM to only users who follow you back. That means now you can DM anybody the only thing you require is a verified twitter account.
For now this service is only available to verified twitter account, they don’t need to follow you back, that enables you to write DM to most of the celebrities and brands-
See this example from @tatadocomo