Nothing wrong with enjoying your sea salt - you'll probably get plenty of iodine from water, flour, milk, eggs, seafood, etc. - but goiters and other mineral deficiency-related diseases happened long before we started making purified salt with chemistry.

http://en.wikipedia.org/wiki/Goitre

> Chinese physicians of the Tang Dynasty (618–907) were the first to successfully treat patients with goitre by using the iodine-rich thyroid gland of animals such as sheep and pigs—in raw, pill, or powdered form.

> Goitre was previously common in many areas that were deficient in iodine in the soil. For example, in the English Midlands, the condition was known as Derbyshire Neck. In the United States, goitre was found in the Great Lakes, Midwest, and Intermountain regions. The condition now is practically absent in affluent nations, where table salt is supplemented with iodine. However, it is still prevalent in India, China Central Asia and Central Africa.