Who cares? Wear your tan lines with pride, or put more sun block on. Shouldn't matter what other people think. If you are worried about skin cancer or something though, that would be a different story. My dermatologist had a short chat with me when he saw my leg tan line last time I went in, pretty much telling me if I have that bad of a tan line I need to be careful and coat myself often because of the massive amount of sun exposure per week.