Must be logged in to email an Instructable to a friend
So, yesterday I updated the site to prevent this from happening again. I changed it so you could only use this feature if you were logged in. We're thinking about different ways to handle it, to still allow people who don't have an Instructables membership to share Instructables with friends, but limit it in some way to prevent anyone from sending spam again. Once we've decided on the best long-term fix, we'll implement it and I'll post about it here.