"Harry Potter and the Half-Blood Prince" opened at 12:01 a.m. today. And the critics are already weighing in?on Twitter. The 140-character reviews are quickly changing the way "word of mouth" works. The Twitterati can tweet their response to a film while sitting in the theater. This is having a dramatic effect on the box office. Sasha Baron Cohen's film Bruno drew $14 million on the day of its release, but was panned on Twitter and sales plummeted 40 percent. Sharon Waxman of The Wrap, and a Takeaway contributor, joins us with a look.