Considering the ground clearance of my OB, I am not concerned about it being hit by something.
When I have removed one in the past, less than 3/4 cup of oil came out, which is an insignificant amount for my 5 quart sump, in my opinion.
Only issue I have had on the 60,000 miles or so I have had it, is the crush washer it came with has started to weep slightly. Not enough to drip, even when the car sits for days at a time, but enough to make the plug area slightly damp with oil.