Not to mention the moments when an author decides to sue the reviewer for a negative review. Being sued for having an opinion is uncomfortable even if you win.
Boring Book Reviews: another in the long series of casualties caused by lawyers run amok.
UPDATE: And the obligatory counter-view: if the newspapers stop reviewing books, people will stop reading them. Can't see that point myself. Virgina Postrel notes that the reviews we are losing are so boring and so uninformative that it's hard to think of people reading them. But she doesn't say why. Lawyers run amok.