Let's start with a basic reminder: the TSA is so incompetent as to be completely and utterly worthless. If there are bombs, weapons, etc. in your luggage, the TSA probably won't find them. They might find a tube of toothpaste that is too large, and haul your ass off to an interrogation room for being a terrorist-dental hygienist, but a gun? No, those ass-clowns won't find it. As the saying goes, they can't find their asses with both hands and a flashlight, which adds special meaning to this scene from South Park...
Anyway, the TSA is worthless. They can't find weapons, bombs, or anything else. If there truly is anything dangerous, they won't find it. That's kind of the point of the laptop bomb. Put a bomb in a laptop, and the halfwit staring at the x-ray of your laptop won't notice anything askew.
As a more general point, whatever rules the DHS and the TSA create are merely inconveniences for the rest of us, unless they create a deterrent effect on terrorists, but that deterrent effect only works if the terrorists are unaware of the fact that the TSA is, as previously stated, worthless and incompetent.
Terrorists can read, so no such luck there.
That brings me back to the pocket knife/laptop distinction. It is possible to disguise a bomb in a laptop, or so we are told. Engineers are clever people. (Just don't tell them that.) A bomb on a plane might not be such a good thing. Of course, a bomb on a train or a bus would be bad too, and taking down a plane with a laptop bomb isn't all that easy, from what I have read (although you should listen to engineers and demolitions experts on that, not me), but still, a laptop bomb on a plane is not a completely bullshit threat. Whether or not it would be worse in the cargo hold, I'll defer to the engineers (but not DHS, or the TSA, who are, again, dipshits of the highest/lowest caliber).
A pocket knife on a plane, on the other hand, is a completely bullshit threat.
This is the point where, if you aren't thinking rationally, you remind me that hijackers brought down the World Trade Center towers and took out a chunk of the Pentagon with box cutters in 2001. Here's the problem. That can never work again. The reason that worked in 2001 was that the passengers on three planes believed that by cooperating, they would live. They thought it was an old-fashioned hijacking, where the terrorists were trying to divert the flight, not use the plane as a weapon. As soon as the passengers on the fourth flight found out what was happening, they rushed the hijackers, and the plane crashed before making it to its destination.
Nobody has ever tried it since, and every time anyone has tried anything fishy since, like when Richard Reid tried to light his shoes on fire, they've been stopped by passengers. Why? Because hijacking a plane with a knife only works if passengers believe that by cooperating, they live. People don't believe that anymore.
They stopped believing it on September 11, 2001, and they won't believe it again. Combine that with the flight crew's attitude, the cockpit doors being locked, and no, you can't hijack a plane with a knife. A knife on a plane is precisely as dangerous as a knife on a bus, subway car, etc. And fuck you if you tell me I can't carry a pocket knife anymore.
And yet, DHS is waiting to do anything on the laptop issue, but they will keep telling me I can't take a pocket knife of flights. Now, I could try to sneak knives through in my carry-on baggage. TSA is, as I mentioned, incompetent, but the risk of losing one of my Chris Reeve knives is not one I am willing to take, much less the risk of losing a full custom knife. I'll throw one of my cheaper pocket knives in a checked bag, because really, everyone should carry a pocket knife. It's a basic tool.
There are multiple levels here, though. What is the risk posed by the items in question, and what is the cost of the ban?
The cost of banning pocket knives is, realistically, not that high. I know that I am kind of a weirdo about this. I got my first pocket knife as a cub scout, and I have carried a knife every day I could since then. Why? As I said, it is a useful tool. It is a stupid weapon (particularly a folding knife), as self-defense experts are better-equipped to explain, but it is a useful tool. Still, the cost to me of either not having one when I travel, or checking a bag, is minimal, and I am capable of performing that calculation.
On the other hand, the cost to the business community of banning laptops would be tremendous. People work on flights. Make that impossible on Europe-US flights and you will have serious problems.
So, this is worth pointing out. We are running higher (although really, still VERY low) risks for allowing laptops in the cabin because the costs of implementing a ban are higher, while maintaining a ban on pocket knives, even though the risks created by pocket knives are basically non-existent because the costs of the ban for the latter are small, but the latter ban gives simple-minded folk some peace of mind.
And of course, none of this matters because the TSA rarely succeeds in its job. If you want to see what they do catch, though, you can get some good deals on cheap-o pocket knives and multi-tools by heading over to eBay and searching for "TSA confiscated." Personally, I am pickier about what I carry, but really, there are some good deals to be had there for the budget-minded folk who want to take advantage of those who forgot to clean out their pockets before heading to the airport. Remember, though, that the TSA failed to find 95% of the banned items planted in bags when they were being tested because they can't find their asses with both hands and a flashlight. Personally, I think they need better flashlights. Currently, I am recommending the Olight S1R for "EDC."
As a final note, I bet the terrorists are sitting around right now trying to figure out how to leak that they are planning on smuggling a suppository bomb onto a plane, just to make that South Park bit a reality. And none of it would matter if people would calm the fuck down about terrorism because that's why they do it-- to get you to freak out. You are more likely to die in a car crash, so stop texting.