My take on the career/careen issue:

The original definition of careen as a verb involved beaching a boat and laying it on its side. It took on the definition of heeling over while under way and then transfered to a land vehicle rocking back and forth, sonething not normally done unless at high speed. It then transfered to simply meaning a land vehicle travelling at a high rate of speed, Career originally referred to a road or track and took on the definition of travelling at a high rate of speed as well as other definitions. When it comes to the modern speaker choosing between career and careen for travelling at a high rate of speed, the alternate definitions of career present a significant obstacle that is not present in the alternate definitions of careen. Almost everyone has, or knows someone who has a career but how many know anyone who has careened a boat?