EDIT: Actually, looks like they went out of business. I'm betting execution didn't match promises.
Artificial gems that try to pass as "real" diamonds have to commit a lot of forgery, not just at the molecular level. Forging the mining certificates, the registration (with GIA, IGS, or other certification services) which actually look at when and where this diamond was mined, etc.
Even if you could perfectly recreate diamonds, you'd find very quickly that selling them for anything other than industrial purposes would be a huge challenge. Jewelers and distributors don't want to piss off DeBeers. Anyone showing up with any kind of volume and quality product that has gone "around" DeBeers somehow would raise far more suspicion than it's worth.
Source: I worked in the jewelry industry for 2 years, and we occasionally had people try and sell us unmarked/unrated diamonds. Totally not worth the trouble.
I thought they made and sold "fake diamonds" that were molecularly indistinguishable from real diamonds nowadays, is that not the case?
*I knew that some people tried to pass them off as diamonds, but after a quick wiki I guess Moissanite always had distinct features from a diamond.