Connundrum: Sunscreen Addiction

Is Daily Sunscreen Application Dangerous?

Since birth, I've been lathered in the sunscreen anytime I venture into the sun. It's what comes with being the freckled spawn of two parents with (benign) skin cancer. Always a fan of the outdoors, my skin has seen lots of sun. You can tell, too. From the lifeguarding, surfing and soccer tournaments, I've definitely notched dozens of sunburns. To protect my skin daily, every morning I apply a moisturizer that includes an SPF 15 sunscreen. 

But now I question whether that kind of chemical exposure is good for me.

Can a daily dose of sunscreen save me sunburn, but give me other problems? 

Does it really manipulate your body's natural production of Vitamin D?

How about the dereliterious effects of metals like zinc oxide?

And finally, does sunscreen actually protect you from melanoma and not just sunburns? 

Sources : http://www.straightdope.com/columns/read/2349/is-sunscreen-ineffective-in-preventing-skin-cancer