This one's going to be a bit of a rant. I'm sure you're overjoyed to read that. But I've just read something that really bugged me, and I was trying to sort out just why that was.
The topic in question was the GUMSHOE mechanic whereby characters are just given the appropriate clues if they investigate a scene - if the Medic examines the corpse then he just gets told about the disparity between the gunshot wound and the time of death, or whatever. Fair enough - I actually think that's a pretty good idea.
But what bugged me was the discussion of the opposite approach, where the player is required to roll, and how a "good GM" will operate in the GUMSHOE manner anyway.
The argument goes as follows: if the ongoing story requires the PCs to find an essential clue, and they have to roll for it, the game comes to a shuddering halt if they fail that roll. Therefore, the GM must either arrange things so the player can reroll until he succeeds, or otherwise arrange for that information to fall into their laps. In effect, he's having to bypass the roll anyway. And, since that just wastes time and generates frustration, the "good GM" will simply skip all that and give the PCs the essential clue.
That's fine as far as it goes, except for one thing: "if the ongoing story requires the PCs to find an essential clue..."
What we have here is a form of railroading. Whatever else happens in the game, the PCs must do something. They must visit a certain location or they must talk to a particular NPC, or whatever. You've created a choke-point in the adventure. To proceed, they must go this way. And each essential clue represents another choke-point - the PCs have to hit A, and B, and C to proceed; all that matters is the order (ABC, ACB, BAC, BCA, CAB, CBA). That's not a railroad in the classical sense, but it's not far off it.
The key thing is that the "good GM" in the roll-for version of the game would not have any essential clues in the first place. Instead, he'd have liberally scattered lots of clues about the place, any of which might or might not be found (but where, statistically, something like 70% will be found assuming 'good' play), and where a suitable subset will give rise to the right conclusions.
And, actually, the "good GM" in the roll-for version would also not require that the players come to the 'right' conclusions anyway. If they decide to proceed against the wrong man, well that's their business - it just leads to another set of circumstances, no more or less valid than the other. (Specifically, it most likely results in the real villain getting away to strike again, the PCs creating a new enemy, and the PCs losing some of their hard-earned prestige. None of which is ideal from this adventure, but in terms of the wider campaign it's not actually all that bad a thing.)
Now, you'll note that I've not said you must play this way. And, indeed, if you are going to have essential clues in the game then I agree you really should just give them to the PCs. I'm just not convinced about the need for essential clues.