No, that would be the free internet draft dork sites that people treat as gospel because they've been logging into them every day for the last 3 months. It's always hilarious when fans fall over themselves on draft day saying "Why did they take him at the end of the first round ... www. fortythreeyearoldvirgindraftnik. com says he would have been there in the 3rd round !!!!", as if that site knows what the hell they're talking about.
As far as having actual insight and information into team boards and GMs, I would put King among the top 2 or 3. But like I said, he's not overly dedicated to the draft. I don't even think King does a single mock until the day before the draft.