Layervault emailed the flat UI creator to ask him to take it down, flat UI refused because they didn't believe their work was infringing. Layervault kept pestering the guy, and eventually he gave up and removed a couple of the icons. And then layervault took this cooperation to be an admission of guilt and sent a DMCA takedown notice.
We in tech need to be good to each other because other corporate interests and patent trolls won't be. We should always give each other the benefit of the doubt and try to resolve issues without menacing legal language and the threat of lawyers. We need to show we can thrive without this garbage. Otherwise, it will only embolden our enemies and cause this type of confrontation to happen more frequently in the future - to everyone's detriment.