Being a former pre-med who has since changed to pre-dental, I agree with many of the points made on this thread (as well as the med vs. dental school admissions thread).
One point that has not been mentioned is that a lot of pre-meds tend to act overly altruistic. They tend to believe that they are being chosen to serve humanity, and nothing must stand in the way of them achieving their destiny. In general, they dismiss any talk of the financial aspects of being a doctor, and claim that they are entering medicine ONLY to "help people"
Unfortunately, this attitude is only exacerbated by the unusual requirements of Med School Adcoms. On my med school interviews, it was mentioned on more than one occasion that simply shadowing a physician was not enough; only by doing excessive volunteer work can one prove that one is capable and ready for the sacrifices of being a physician. This attitude trickles down to pre-med advisors and ultimately to applicants, who then convince themselves that you can only enter medicine if you've been volunteering since high school. And then this fuels the "I am holier than thou" attitude that many pre-meds have. It is a vicious cycle.
Overall, I find dentists and the pre-dental community to be a lot more laid back and more practical than pre-meds. When people on this board post about the financial benefits of going to perio or ortho, no one jumps on the poster about being "in it for the money." Everyone on this board has a legitimate interest in working with people and contributing to their patients' oral health, but not to the point where we feel that we've been chosen by God to become a dentist...
Just my $.02 on this subject.