They are pointless if someone lies, but I think they can be useful if they are used as part of a larger eveluation process. In grad school we actually took tests like that (Myers Briggs) with our group that we worked with for our senior thesis - it was interesting to see that some of us were complete opposites in terms of how we organize, study, learn, and approach task management.
i think most people lie when they take those tests. if they do tell the truth, then i believe that they can be a helpful tool in selecting a new employee.
Those things are totally bunk! No on is really honest with their answers anyway. People answer the questions based on how they "would like" others to see them.
If employers want a true test, have them give the test to your best friend and worst enemy to evaluate you. Then average them out and you got YOU in a nutshell!!