It would be interesting to hear more about potential evidence linking sun exposure and sunscreen to malignant melanomas as opposed to basal and squamous cell carcinomas. BCCs and SCCs, while malignant, do not pose the same risks of metastasis as melanoma, so I would be much more inclined to alter my behavior given such evidence.

In general (but not always) I like to assume that balance is the key. Life is carcinogenic, and too much of anything is probably harmful.