UPDATE: It seems like it really is true. The LA times now reports that Jackson was pronounced dead by doctors. BBC News is also reporting his death, along with MSNBC, and the Associated Press. CNN has so far not confirmed his death.
Previously:
It’s a rough day for 80’sd idols. We’ve just heard that after Farrah Fawcett died of a long standing battle with cancer, Michael Jackson has died of cardiac arrest, says TMZ.com. CNN, however, reports he was taken to the hospital following cardiac arrest but will not confirm his death.
More details to follow in a few minutes.
From TMZ: 
Michael Jackson Dies
We’ve just learned Michael Jackson has died. He was 50.
Michael suffered a cardiac arrest earlier this afternoon at his Holmby Hills home and paramedics were unable to revive him. We’re told when paramedics arrived Jackson had no pulse and they never got a pulse back.
A source tells us Jackson was dead when paramedics arrived.
From CNN:
Sources: Michael Jackson taken to hospital after cardiac arrest
(CNN) — Entertainer Michael Jackson was taken to a hospital on Thursday after suffering cardiac arrest, sources briefed on the situation told CNN.
A Los Angeles fire official told CNN that paramedics arrived at Michael Jackson’s home after a 911 call.
Paramedics revived Jackson before taking him to the hospital.
Fire Capt. Steve Ruda told CNN a 911 call came in from a west Los Angeles residence at 12:21 p.m.
Ruda said Jackson was treated and transferred to the UCLA Medical Center.
Asked specifics of the patient’s condition, the spokesman said he could not discuss them because of federal privacy laws. The music icon from Gary, Indiana, was known as the “King of Pop.”
Jackson was the seventh of nine children in a well-known musical family.
BBC Streaming video and coverage:
It's been confirmed.
http://www.msnbc.msn.com/id/31552029/ns/entertain…
A Myspace blog response for MJ's ex Lisa Marie Presley: http://blogs.myspace.com/index.cfm?fuseaction=blo…
He Knew.
Years ago Michael and I were having a deep conversation about life in general.
I can't recall the exact subject matter but he may have been questioning me about the circumstances of my Fathers Death.
At some point he paused, he stared at me very intensely and he stated with an almost calm certainty, "I am afraid that I am going to end up like him, the way he did."
I promptly tried to deter him from the idea, at which point he just shrugged his shoulders and nodded almost matter of fact as if to let me know, he knew what he knew and that was kind of that.
14 years later I am sitting here watching on the news an ambulance leaves the driveway of his home, the big gates, the crowds outside the gates, the coverage, the crowds outside the hospital, the Cause of death and what may have led up to it and the memory of this conversation hit me, as did the unstoppable tears.
A predicted ending by him, by loved ones and by me, but what I didn't predict was how much it was going to hurt when it finally happened.
The person I failed to help is being transferred right now to the LA County Coroners office for his Autopsy.
All of my indifference and detachment that I worked so hard to achieve over the years has just gone into the bowels of hell and right now I am gutted.
I am going to say now what I have never said before because I want the truth out there for once.
Our relationship was not "a sham" as is being reported in the press. It was an unusual relationship yes, where two unusual people who did not live or know a "Normal life" found a connection, perhaps with some suspect timing on his part. Nonetheless, I do believe he loved me as much as he could love anyone and I loved him very much.
I wanted to "save him" I wanted to save him from the inevitable which is what has just happened.
His family and his loved ones also wanted to save him from this as well but didn't know how and this was 14 years ago. We all worried that this would be the outcome then.
At that time, In trying to save him, I almost lost myself.
He was an incredibly dynamic force and power that was not to be underestimated.
When he used it for something good, It was the best and when he used it for something bad, It was really, REALLY bad.
Mediocrity was not a concept that would even for a second enter Michael Jackson's being or actions.
I became very ill and emotionally/ spiritually exhausted in my quest to save him from certain self-destructive behavior and from the awful vampires and leeches he would always manage to magnetize around him.
I was in over my head while trying.
I had my children to care for, I had to make a decision.
The hardest decision I have ever had to make, which was to walk away and let his fate have him, even though I desperately loved him and tried to stop or reverse it somehow.
After the Divorce, I spent a few years obsessing about him and what I could have done different, in regret.
Then I spent some angry years at the whole situation.
At some point, I truly became Indifferent, until now.
As I sit here overwhelmed with sadness, reflection and confusion at what was my biggest failure to date, watching on the news almost play by play The exact Scenario I saw happen on August 16th, 1977 happening again right now with Michael (A sight I never wanted to see again) just as he predicted, I am truly, truly gutted.
Any ill experience or words I have felt towards him in the past has just died inside of me along with him.
He was an amazing person and I am lucky to have gotten as close to him as I did and to have had the many experiences and years that we had together.
I desperately hope that he can be relieved from his pain, pressure and turmoil now.
He deserves to be free from all of that and I hope he is in a better place or will be.
I also hope that anyone else who feels they have failed to help him can be set free because he hopefully finally is.
The World is in shock but somehow he knew exactly how his fate would be played out some day more than anyone else knew, and he was right.
I really needed to say this right now, thanks for listening.
~LMP
there would be no other King of Pop like Michael Jackson. he would always be the King.