I was discussing sauerkraut recipes with someone on IRC a minute ago, and they warned me not to use iodised salt to pickle the cabbages. My first (and so far, the only successful) batch is one I made with iodised salt - I think it's pretty much the default here. Searching the Internet shows roughly equal numbers of answers going either way, from "it doesn't matter" to "it discolours the vegetables" to "it kills the bacteria you want".

Clearly elemental iodine is nasty, as are any of the halogens. But is the iodide ion similarly harmful to the yeasts and bacteria involved in pickling, in the low quantities in which it's present in supermarket salt?