I think that at the end of the day, when it comes to people copying your design, you really need to take the emotion out of it. I've had my design work copied before, so I know that there is an emotional response that comes along with having your work copied. But there also needs to be a practical assessment of what impact the copying will have on your business. If the site(s) copying you aren't big names and aren't competing with you, it's likely a waste of your time and energies to be pursuing them. That's time being taken away from your core business to focus on other people that ultimately have an inconsequential impact on your ability to be competitive and make money.