Couldn't help but notice this thread while lurking. I work in the pharmacy at a large teaching hospital, and in my experience in working in the outpatient sector, I've had a couple residents and a couple old geezer MDs write for themselves or their SO.
AFAIK, no one really cared all that much as long as it was something relatively common. Most of the stuff was pretty innocuous, like statins or HTN meds or BC, and half the time it was written because they just needed new refills.
I can see the POV for the slippery slope, but I can't think of anything more innocuous than writing yourself a refill for lipitor or metoprolol. Besides, even if someone was gutsy enough to try and get ativan or something controlled, 99% of pharmacists will refuse.