It's becaused they misused the DMCA to force removal of content that, while inspired by them, they actually don't own the copyright of. Vis., they are using the DMCA illegally to remove legal content.
I'm not sure how they "misued" the DMCA. The law has specific mechanisms for notifying a hosted service of material which violates your copyright. If LV believes the work violates their copyright, they're well within their rights to request it be taken down.
You might like the draconian nature of the laws mechanisms but it's not a "misuse". It's just "I don't like it when people use it."
They misused the DMCA because they did not own the copyright of the content they filed a DMCA against, plain and simple, and they made specific claims in the DMCA otherwise. Just because the icons were similar does not make that a copyright violation. LV either abused the DMCA out of ignorance or dishonesty. There is no other possibility here, and they deserve every bit of negative sentiment that has resulted against them.
Again, you and LayerVault don't seem to understand copyright.
Here's an example. There's a famous iPhone game called Fruit Ninja. There's another game called Veggie Samurai. Total ripoff in every imaginable way, but completely legal.
Copyright means you can't make direct copies or derivative works of my stuff. It doesn't mean you're not allowed copy all my ideas.
The DMCA is for direct copies of IP. This dispute is better resolved with a civil court case because the ownership is non-obvious. It was a very clear misuse of the DMCA and I hope the victim receives some compensation.
I have yet to see any evidence that the Flat UI folks violated any copyrights. It doesn't look like the Flat UI guys made verbatim copies of any of LV's art, nor does it look like they took LV's art and altered it to hide its origins.
It looks more like someone came from the viewpoint of "let's make some icons like LayerVault's," which may or may not be an IP violation, but it certainly is not a violation of copyright.
If LV knows differently, they certainly don't appear to be interested in telling us how they know, hence the pitchforks.
