Really? Most jobs? Things must have really gone downhill in the U.S. since I left for Germany (where I have never heard any of my colleagues or acquaintances mention such testing).
Requiring invasive medical procedures (blood samples, hair samples, etc.) or humiliating ones (urine samples) as a precondition for employment is an ethically quite troubling issue. With the exception of airplane pilots and such, I (personally) would lean towards banning any such requirements. Then there is also the secondary issue of data security and confidentiality (what other values - besides my degree of sobriety - are being measured, stored, and/or distributed, and for how long?).
I suspect that I would fail a standard test for opiates in the blood, since I eat a whopping slice of Schmandkuchen mit Mohn every day. I guess the solution would be to illegalize those, too.
Regards,