In Germany (and most probably in a lot of other places as well), you are legally obliged to publish the contact details for any commercial company website you are publishing. Then, the malign harvesters rummage around and collect this information to spam you. Annoyed? Well, then here is the remedy: Generate a captcha from your contact details. Humans can read it, bots shouldn’t be able to. This would be about the first time, a Captcha made sense…