I agree with you bfb, my missus is a psych and makes a heap of money doing these tests for a range of employers. Helps with the mortgage and amuses me with the results. She would be the first to tell you they are at best a Guide to an individual, at worst a complete waste of time. In her early days she has experimented on me with these things to try manipulate results and see if she is with a madman. There was a consistancy with them even with my studied tweaking efforts.
I remember a job where we had to do a heap of mil spec tests designed by the forensic psych institute, a big player in the government market. A few people who I thought were a bit on the crazy side got through and a couple of top blokes who would have been good didn't. The kicker was the full day of "team building exersizes" with 3 psych's watching, taking notes. This did weed out the suspect crazies and we were left with a number of people who fit the bill.
I think if companies are using them as a primary employment tool they are losing some good people and maybe picking up the odd switched on sociopath. Best to use people with people and a good interview.