Yes, the commercial use of personal information, in the way that Facebook uses such information, is unethical. A person has a reasonable right and expectation to privacy, even when using a third party service. Thus, Facebook is committing an unethical act by selling that information to advertisers for targetted advertising.
I believe that commercial use of personal information is unethical, particularly when done without consent of the person. Facebook is known to misuse personal information by displaying advertisements for products as if they were endorsed by a user, who generally has no idea that his or her profile is being used to advertise the product. This practice is unethical because the endorsement is not actually coming from the user and the users friends are mislead into thinking that their friend is endorsing something.