You can call it vanity, insensitivity, idiosyncrasy, or just simple idiocy. Celebrities getting embroiled in controversies aren't rare on Twitter. All it takes are some 140 characters or a single image tweeted to thousands of followers. In most cases, the celebs were not aware that the pictures they were linking to, through their tweets, were not appropriate. Most of them apologize and move on with their lives. And very rarely they delete Twitter accounts altogether.
