It details the Smoke Filled Room in which, 20 years ago, Rap music was turned to the Dark Side. Here's the site, O'Finoian's Blog. Charlie Stross apparently got the same notification, and his link goes here, but it's the same.
Here's a few excerpts:
After more than 20 years, I’ve finally decided to tell the world what I witnessed in 1991, which I believe was one of the biggest turning point in popular music, and ultimately American society. I have struggled for a long time weighing the pros and cons of making this story public as I was reluctant to implicate the individuals who were present that day. So I’ve simply decided to leave out names and all the details that may risk my personal well being and that of those who were, like me, dragged into something they weren’t ready for.
Quickly after the meeting began, one of my industry colleagues (who shall remain nameless like everyone else) thanked us for attending. He then gave the floor to a man who only introduced himself by first name and gave no further details about his personal background. I think he was the owner of the residence but it was never confirmed. He briefly praised all of us for the success we had achieved in our industry and congratulated us for being selected as part of this small group of “decision makers”. At this point I begin to feel slightly uncomfortable at the strangeness of this gathering. The subject quickly changed as the speaker went on to tell us that the respective companies we represented had invested in a very profitable industry which could become even more rewarding with our active involvement. He explained that the companies we work for had invested millions into the building of privately owned prisons and that our positions of influence in the music industry would actually impact the profitability of these investments.
Our job would be to help make this happen [increase in prison population] by marketing music which promotes criminal behavior, rap being the music of choice. He assured us that this would be a great situation for us because rap music was becoming an increasingly profitable market for our companies, and as employee, we’d also be able to buy personal stocks in these prisons.
It's an interesting read. I don't think it's true, as I don't believe that an unvetted bunch of "decision makers" could be invited to such a meeting, and then when some of them express disbelief, armed men get rid of them, but after that nothing bad happens and no-one speaks about it for twenty years. But it's certainly true that private prisons have taken off, and it's certainly true that an unbelievable number of black men are incarcerated in them. The prison staff agitate for longer sentences for inmates, for three strikes laws; the owners use the men for indentured servitude. It's a terrible, third world, evil, system but I can't see that Rap musicians were bamboozled into being its midwife.
On the other hand, Rap did change from responsible to gangsta - but not quite at that time.
Early Rap music continued in the tradition of such groups as the Last Poets (as heard in the soundtrack of 1970's Performance). They were beat poets, speaking in a didactic tradition. Funkier folks kept to the wisdom/anti-drug/community improvement line as well; White Lines, by Grandmaster Flash, being the index example.
Much hip-hop was more playful, like the accomplished and sample-heavy 3 Feet High and Rising, by De La Soul - funny and clever.
Three Is The Magic Number, De La Soul.
I still listen to it today. I still listen to KRS-One (Boogie Down Productions), where he exhorts, "You Must Learn" - and although it turns out in Why Is That, that much of what you must learn is a sort of origin myth about the sons of Noah that doesn't seem to hold up, it's still not a bad thing to ask young kids to learn, black or white. Back around the same time, Public Enemy were telling young black kids to listen to Dr. King. When Ice-T sang I'm Your Pusher, he was talking about music, not about drugs - something that seems to have escaped most people. His album, Rhyme Pays, was the first hip-hop album to carry an explicit content warning.
The crime rate was rising rapidly in the late eighties, and hip-hop began to reflect that. Suddenly - Bingo! - white kids who could care less about Martin Luther King, or the genealogy of Shem, or Ham, whichever name KRS-One had picked as the father of black-kind  - were given a subject they cared about, sex and violence. Rap sales took off into the stratosphere, and Gangsta rap, not coincidentally, took off at the same time. By 1992, the crime rates were falling again, but testosterone-addled adolescents continued to be interested in the life of a gangsta. I'm not going to guess at whether they thought black people were naturally more prone to violence so it was 'safe' to listen to them talk about their experiences, real or faked, or whether the kids just liked violence - the success of Michael Bay et al suggests that it's the latter, but whatever.
One of my favorite hip-hop albums is NWA's Straight Outta Compton. It's funky, and it's hilarious in parts, and it's filled with violent images - it was also released well before the conspiracy theory says powerful white men in a smoke-filled room got together in 1991 to turn rap into a money-making proposition for the prisons.
So, myth busted, I believe. Still love that 80's hip-hop though, and I think it's a shame it changed.
Here's Wise Intelligent of the Poor Righteous Teachers giving his view (pre-conspiracy theory). He describes the pressure on rappers from record companies to make 'negative hip-hop'.
 I can't tell what he's saying on the record. In the bible, Shem was the father of Semites (Jews and Arabs), and Ham the father of black Africans - if, as KRS-One does, you believe black Africans are Israelites, this is confusing. Having met a fair number of white non-Jewish Israelites, I can categorically state it's not the most confusing genealogy out there.