That said, I didn't realize "going outside with short hair and no hat" was a bad lifestyle choice until it was too late, so I'm posting here:
Hey fair skinned folks! Just wearing sunscreen IS NOT ENOUGH. Wear a hat if you're going to spend more than a short time outside! If you have a family history of skin cancer, ask your barber to keep an eye out for moles when you're getting your hair cut.
http://greathealinggetaways.com/Sunscreenarticle.html
Sunscreens often contain carcinogens:
http://en.wikipedia.org/wiki/Potential_health_risks_of_sunsc...
Consequently staying indoors and using sunscreen may _increase_ your likelihood of developing cancer.
Children who avoid sunshine will get rickets, a disease that was once almost absent from the US population:
http://www.telegraph.co.uk/health/healthnews/8128781/Middle-...
Nonetheless, the fair-skinned must balance their exposure carefully. Good news is that their skin produces vitamin D more efficiently than darker skin, so the fair-skinned can obtain vitamin D in a shorter exposure period (minutes a day):
http://www.usatoday.com/news/health/painter/2009-04-19-your-...
http://en.wikipedia.org/wiki/Hypovitaminosis_D#Cancer
That said, if you are going to spend time outside, the benefits of wearing sunscreen and a hat undoubtedly outweigh whatever risk they may induce.