I think the biggest problem with most NFL mock drafts is that they contain little to no knowledge of the teams that are actually doing the drafting.
It's one thing to criticize Mel Kiper or Todd McShay for mis-judging an NFL player or prioritizing the wrong skills or advantages. That's become almost a sport of its own. And please understand - every one of these guys probably knows just how silly it is to write mock drafts before the Combine even happens, much less in September. They get that. If you're irritated by early mocks, you can probably blame editors and number-crunchers who are thinking about page hits, as well as draft junkies who are willing to provide those hits even if it is September.
But really, once you get a layer deep, even the April mocks just don't seem to have any idea about the teams themselves. They're written up without any knowledge of what the team needs and how badly, who the team already has and how good they are, how the team's general manager thinks and what he values, and what picks might best fit the scheme and play style of the team in question.
And without answering those questions, is anyone really qualified to guess who will pick whom?
You've got your "big boards", sure. Those abstract lists that dodge the issue by ranking players by value instead of selection. But is that really what people want to know? My guess is no. They want to know what will happen on draft day, who will pick whom. There's a psychological pull to that - the draft is an exciting mix-and-match game to begin with - and a practical pull: there's no point getting excited for that shiny new quarterback if another team is going to grab him. A lot of "big boards" probably get either mis-read as mock drafts anyway, or taken and turned into mock drafts by clever readers.
Which is why you have to know the teams. Take Seattle in 2009, when their #4 choice was winnowed down to three top options: QB Mark Sanchez, WR Michael Crabtree, and LB Aaron Curry (in order of importance of position).
There were plenty of people who picked Curry for Seattle, but why? Because he was an impact player, because he was generally a top-five pick, and because people had a vague idea that Seattle GM Tim Ruskell had just traded Julian Peterson and left a bleeding hole at OLB. Fair reasons, but superficial. Sanchez and Crabtree were mocked to Seattle by some, but only because of a superficial knowledge that Seattle had no wide receivers and no successor at quarterback. Not a lot of depth or insight to that kind of judgment.
And none of it really showed a knowledge of Tim Ruskell at all. Any 2009 draft watcher who knew Ruskell knew beyond a doubt that Curry would be the pick. Curry was a "safe pick", a four-year college player who produced. He had a terrific work ethic and no character flags. He attended a big school. He was a defensive guy, bent more towards run defense than pass defense. He was expensive, but Ruskell didn't mind overpaying players. And perhaps most tellingly, Curry was the guy Ruskell had stayed the quietest about in the months leading up to the draft.
Boom - Ruskell pick.
That's what I want from mock drafts: GM profiling, in-depth team knowledge, and real behind-the-scenes intel. Nothing these "insiders" say makes me believe they actually have inside sources, except to say that they have inside sources. If you want to get a finger on the pulse of the draft, they can tell you what's going on behind the mock-borrowing and guesswork that others do, I recommend Rob Rang of CBSSports.com, Tony Pauline of Draft Insider.net, and Rob Staton of Seahawks Draft Blog. Staton has the extra advantage of being particularly tuned in to the Seahawks. It is way easier, in fairness, to mock for one team than for all 32.