It's almost like what happens to Mercedes Benz. Companies like Mitsubishi shamelessly copy MBZ designs. They've been doing it for years. MBZ's answer is to continuously innovate.
Obsolete you own product.
That's the whole point of patent and copyright law. They're defenses against locusts. The fact that these laws have been abused and need reform should not obscure their underlying value and purpose, which is actually becoming clearer than ever.
"Constantly reinvention" is just total bullshit when you start talking about salt and pepper shakers. And so is the idea of "staying ahead of the curve" when doing so means a non-stop torrent of additions to landfills everywhere. Good designers get this. They're actually very resourceful people who are trying to make the world work better in ways both small and large. Squandering resources with a stream of pointless variations doesn't square with this ethos at all.
The difference between design and trash is that good design is what you hold onto for years, even generations. What the best designers strive for is the elegant solution, a perfect convergence of form and function that resists further change for as long as humanly possible.
Again, the opposite of fashion.
Since the web is a place where things are very easily copied, it stands to reason that good ideas will be emulated and this is to be expected.
It would seem quite contrary to the idea of the web to give a single entity a monopoly on laying out a page in a particular way.
If you do, you'll see that we're not talking about general conventions here (e.g. the similar layouts of YouTube and Kickstarter pages). Nor is this "emulation" in many cases. It's just unvarnished theft (i.e. using the same copyright protected photos as backgrounds).
Best thing to do is to send the owner a Cease & Desist letter, and if they're based in the US, a threat to have the site pulled by the webhost under the DMCA in the event that the owner refuses to comply. It's diplomatic to give the owner a way to save face be acknowledging that that may also be getting victimized by an unscrupulous third party who is passing off the work of others as their own. But also note that this doesn't change the facts of the matter, and state that, one way or another, the site must come down immediately.
You shouldn't say or offer anything else until they call you back and offer you a chance to gauge their demeanor. Chances are good, they're going to be angry. Question is, at who? If it's with you (for ruining their day) then fuck 'em. They're not the kind of people you want anything to do with. Just tell them they have 24 hours to comply or you'll have the site pulled for violating copyrights, and that you won't release the claim unless they pay you several thousand dollars. However, if they're reasonable, they'll be angry with their vendor, apologetic with you, and then you can turn the exchange into a sales call.
Also, there's a legal concept called trade dress, which protects the signature elements of a product. Mitusibusi copies Mercedes, but only to point. And that point is defined by law. This law explains why the imitations are so pale, and why the markets for Mitsubishis and Mercedes have so little overlap.
That doesn't mean that Mercedes can stagnate. It's a design icon, after all, and has to fit within a larger sphere that is always changing. But protection for its brand does mean can move at a more considered and deliberate pace (good conditions for thoughtful, lasting design), then it could if competitors could make perfect copies with no appreciable latency.
Slow moving design is a feature, not a bug. You'll note that cars that hit on a relatively unchanging design that doesn't date itself quickly have higher resale values than those that don't (like, ahem, Mitsubishi).
Mitsubish are selling product, while this is a portfolio design and thus should require less attention while you work on clients.
The solution is not to blame the victims of the theft. Agreed that shaming isn't always the best idea either though.