Hey, have you voted yet? No? Then what are you doing reading this post? If you have time to surf the Internet, you have time to vote. Go vote, then come back and read this later. Thanks.
Okay, let me say this first: I find bald men who embrace their baldness -- by shaving their heads or keeping their hair very short -- extremely attractive. There's a confidence that goes with being fearlessly bald that no well-coiffed man can hope to achieve. And nothing is sadder than the men who cling to those last strands of hair, combing them sideways or forward in a losing effort that fools no one. Give it up, guys, and let your light shine (off the tops of your heads).
Without having access to your medical records, Sean, I'm guessing that your hair loss is a case of standard male pattern baldness, or androgenetic alopecia (androgenetic = related to masculinity, alopecia = hair loss). This is an genetic trait that, contrary to conventional wisdom, can be inherited from either the mother's or the father's side. Everyone's hair falls out all the time; what happens in male pattern baldness is that these hairs don't get replaced, because high levels of a hormone called dihydrotestosterone (DHT) cause the hair follicles to shrink and become inactive. Weirdly, this hormone only affects the follicles on top of the head, so hair on the rest of a man's body, up the neck and to about the tops of the ears, can grow as bushy as ever. (In these cases, I highly recommend judicious use of a razor.)
Baldness in primate species is the mark of the alpha male, and -- perhaps counterintuitively -- makes men look younger, after a certain point. A good friend of mine has been bald for as long as I've known him, going on 20 years now. Twenty years ago, at the age of 29, he looked ten years older than his age; now, as he approaches 50, he looks ten years younger.
People can lose their hair for other reasons besides male pattern baldness, so anyone who experiences sudden hair loss should go see a doctor. Nutritional deficiencies, exposure to radiation or certain poisons, and some serious illnesses can all cause sudden hair loss. Baldness can also be caused by alopecia areata, an autoimmune disease that can cause hair loss not only on one's head, but anywhere on the body. (Since you have eyebrows, Sean, I'm guessing this isn't your problem.)