Should Employers Be Allowed to Use Personality Tests on Prospective Employees?

A recent article highlights the surge in use of personality tests by employers to assess the personality, skills, and cognitive abilities of prospective employees. At the same time, there has been increased concern whether such tests discriminate against people with disabilities (e.g., individuals suffering from mental illness like depression or bipolar disorder). What are your thoughts? Do employers have the right to use such tests in their hiring decisions?
http://online.wsj.com/news/article_email/SB20001424052970203293204580113700174424226-lMyQjAyMTA0MDAwMjEwNDIyWj