Yahoo recently put up an article on sunscreen and how it increases skin cancer.  It confirms several points I've found in digging around the online medical journal studies:

• sunscreen does not protect against melanoma
• relying on sunscreen instead of covering up or managing sun exposure increases skin cancer risk
• our bizarre habits of semi-nudity at beaches are the cause of most of our skin damage
• many sunscreens break down in the sun, some begin in just 15 minutes
• most people use nowhere close to enough sunscreen to provide the claimed SPF level, anyway
• chemicals in sunscreen cause DNA damage and may contribute to cancer, including skin cancer

(The EWG referenced in the article is the consumer group responsible for the Skin Deep Cosmetics Database linked in my other posts on sunscreen.)

Concludes the Yahoo article (from LiveScience.com):  "We merely think we are protected; few really are."

ETA: Link has gone; here's the original from LiveScience.com.