While random tests ideally seem like a good way to keep a drug-free work space, in reality the idea is flawed because a lot of times the tests aren't random at all! that's what makes these tests an invasion of privacy.....
Since no one really is regulating private employers adminsitering random tests, these employers can use random tests as a tool, manipluating the "randomness" to weed out (no pun intended) unfavorable employees. Furrthermore, some higher (again no pun intended) employees may be purposely excluded from the tests. Here's another scenario- Can you imagine if you were up for retirement after giving 20 years of service to a company and then suddenly being given a random drug test- it might be an easy way for a company to get out of giving you're pension. Until there are rules that employers cannot bend, so called "random"-testing is unfair to the employee!
Furthermore, random-testing gives an advantage to drug users who take narcotics, heroin and harder drugs as these drugs typically are undetectable after a couple days. While the occasional pot smoker can get busted smoking once in a blue moon.
Here's one more thing to chew on- kind of off-topic but oh well- how the hell does a professional basketball player, who is a role model for children get suspened for a game or 2 for a positive drug test???? while a regular 9-5er trying to support a family, smokes a little weed here and their- gets fired! Oh yeah, that's right, corporations make the laws haha