Many of my commenters seem to think that the point of the Gaza blockade is simply to keep war materiel from reaching insurgents in Gaza.  That is not the reason for the Gaza blockade, though it may be one goal.  But the strategy is much farther reaching than that:  it is to topple Hamas by immiserating the people who elected them.  Check out some of the war materiel being blockaded:

I know that terrorists can be fiendishly clever, but there is no real evidence, only unconfirmed rumors among the intel community, that Hamas actually has the Coriander Bomb. Most experts put them at least 5-8 years away from developing that sort of destructive technology.

Peter Beinart elaborates on the strategy:

The Conference of Presidents of Major American Jewish Organizations greeted news of the flotilla disaster by repeating a common "pro-Israel" talking point: that Israel only blockades Gaza to prevent Hamas from building rockets that might kill Israeli citizens. If only that were true. In reality, the embargo has a broader and more sinister purpose: to impoverish the people of Gaza, and thus turn them against Hamas. As the Israeli newspaper Haaretz has reported, the Israeli officials in charge of the embargo adhere to what they call a policy of "no prosperity, no development, no humanitarian crisis." In other words, the embargo must be tight enough to keep the people of Gaza miserable, but not so tight that they starve.

This explains why Israel prevents Gazans from importing, among other things, cilantro, sage, jam, chocolate, French fries, dried fruit, fabrics, notebooks, empty flowerpots and toys, none of which are particularly useful in building Kassam rockets. It's why Israel bans virtually all exports from Gaza, a policy that has helped to destroy the Strip's agriculture, contributed to the closing of some 95 percent of its factories, and left more 80 percent of its population dependent on food aid. It's why Gaza's fishermen are not allowed to travel more than three miles from the coast, which dramatically reduces their catch. And it's why Israel prevents Gazan students from studying in the West Bank, a policy recently denounced by 10 winners of the prestigious Israel Prize. There's a name for all this: collective punishment.

Israel does not deserve all the blame for Gaza's impoverishment. Gaza's other neighbor, Egypt, imposes an embargo of its own, though less effectively. And Hamas has been known to confiscate goods meant for Gaza's poor.

There is also an active and delightful industry in Israeli companies lobbying to get the blockade lifted for their products whenever sales dip.

You can justify this on military grounds, of course, though I won't; I think collective punishment is never warranted, and sieges rarely, and certainly not in retaliation for rocket firings that killed, IIRC, one Arab, and the kidnapping of a single Israeli soldier.  And I certainly agree that Israel's critics do not lavish enough attention on Egypt's enforcement of the same blockade, though Egypt does let the leash slip every now and again. 

But whether or not you agree with the policy, this was not particularly about keeping Hamas or other groups from getting weapons--the "weapons cache" found aboard consisted of knives, slingshots, and wooden batons, which pose no threat to Israeli civilians even if they make it to Gaza.  This was about control. And it backfired badly as the crack Israeli troops either opened fire on a poorly armed group of civilians, or, alternatively, moronically dropped one-by-one into a violent mob of poorly armed civilians and got their sidearms taken from them.  Either way, they did not get the overwhelming display of control that they were clearly seeking; instead they got this graphic, which has been making the rounds in military and defense circles:

You cannot understand the Israeli-Palestinian conflict if you are determined to believe that every single thing one of the two sides does is the brilliant and imminently necessary exigency of an existential conflict, the brilliance undone only by the perfidy of a biased media that refuses to tell the true story. People, especially large groups of them, are more complicated than that. And both sides in this conflict are attempting to play a long game. To my mind, at this point both of them are playing extraordinarily badly. But that's a blog post for a different day.