Last month there was a stir about Urban Outfitters stealing a design from an Etsy designer. While Regretsy may not be popular with everyone, the blog's author pointed out that the Etsy artist wasn't the first to create the design in question in this post.
I also found a very informative article on Crafting an MBA that explains why "You can't copyright an idea and you can't copyright a useful object." The author, Megan Auman, starts out discussing the Urban Outfitters story and goes on to explain that the US government sees jewelry as a useful object and will not give it copyright protection.
Do you make clothes? The government also sees clothing as a useful object and here's a great video on "how the lack of copyright and patent protection for clothing design has accelerated the creative pace of the fashion industry."
So what to do? I liked what Megan Auman had to say about it: "Your biggest concern shouldn't be getting your ideas stolen, it should be obscurity." and "If you're really concerned about being copied, the best thing you can do is be innovative."