Check out Twitter feeds and you will notice political statements inserted in any celeb account. It is not the celebs that did it but Twitter or Media Matters themselves.
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You mean just tweets addressed to celebs or posting tweets that appear as posts from given celebs?
“...that appear as posts from...”
See: Daily Mail: Barack Obama has 19.5M Fake Twitter Followers [Analysis from 2013]
http://www.freerepublic.com/focus/f-news/3553932/posts
Excerpt: Of the president’s 36.9 million Twitter followers, an astonishing 53 per cent – or 19.5 million – are fake accounts
Twitter has been a scam from day one.