Sure, they can assist in product development and customer service tweaks with their comments but any complaints they might have will also be magnified and broadcasted a thousand-fold as well.
The time it takes for sellers to build a good reputation and a high level of brand trust on any service platform is crucial because a verified history of good feedback and comments is essential for any customer to make an informed choice.
Update: As Megan Kretz of Running Shorts points out in the comments, a smarter corporate strategy for responding to negative tweets is to reach out to the Twittering customer, rather than serving them with a lawsuit.