I won't invest in drug development companies where I think there may be a psychological effect on the patient getting "better". I just think these companies are seriously compromised by a placebo-effect.
Therefore, I play Russian Roulette with oncology companies where, at the very least, I can see scans, follow patients, and look at pictures and see, what I feel, is working, or isn't working. You can't have a placebo-effect on holes in people's bodies closing up ala GDC449 or Ipilumumab.