The reality is, we WILL eventually forget. As far as catastrophes go, 9/11 is small potatoes (when you count lives lost, levels of destruction, mayhem, etc).
What happened? Two airplanes flew into the world trade center buildings, one crashed into the pentagon, and one crashed into a field. Overall, ~3,500 lives were lost. It's a tragedy, without a doubt, due to the preventable loss of human life. Yet, the firebombings of Dresden, Tokyo, and a swath of other cities killing hundreds of thousands and leveling ALL infrastructure barely registers a reaction. Equally disasterous to the firebombings is the more salient nuclear bombings of Hiroshima and Nagasaki, which pretty much had the same effects as the fire bombings but was instantaneous and more psychologically shocking. Or perhaps, we should also never forget the millions of people purged at the hands of Stalin, or the hundreds of thousands of Kurds gassed at the hands of Saddam Hussein and his chemical weapons. Right NOW, thousands of people are dying in Syria, neighborhoods are being shelled every day, and homes are being destroyed. It's already more catastrophic than 9/11/2001, yet the depressing response is "meh... it's in the middle east with a bunch of crazy hotheads.". Why choose 9/11/2001 as a day to remember due to the catastrophe when there are so many catastrophes more worthy of remembering? Perhaps, it's the recent proximity in history? Or maybe it's not as psychologically routine like regular bombings or an ongoing war? Whatever the case, I hope to GOD that it isn't due to some sense of American exceptionalism, where we think American life and property is orders of magnitude more valuable than other life and property. Human life is human life, regardless of nationality or citizenship status (an invading fleet of extraterrestrials wouldn't make any distinction between one person or another).

Anyways, as far as the disaster is concerned, we will eventually forget it based off of historical trends.
The japanese surprise attack on pearl harbor is the closest historically similar event to 9/11/2001. How fresh is that wound? Do we take a moment of solemn silence and reflect on that every December 7th, or do we say "meh..."? Or how about the sinking of the USS Maine in Havana harbor, which cued the headline "Remember the Maine!"? Do we remember the Maine like we're asked to? We eventually shrug our shoulders and carry on. We have to, because otherwise we'd be inundated with disasters to remember and little would get done. The world is a cold, hard place where it is completely unconcerned about the affairs of people. It'll keep spinning on its axis passing its days whether we're here or not, whether we're butchering each other or not, or holding hands and singing kumbayah or not.

The bottom line is that we will forget 9/11/2001 as it too eventually sinks into the oblivion of distant history in the back pages of a book, eventually dwarfed by fresher and more shocking disasters to come.

+1 to slayemin, it's a tragedy, but pales in comparison to some of the horror's throughout history, that barely get a page in a history book.

edit: also, don't understand why the picture has a "Imagine no religion" text over it.

It's quite likely that the OP is just trolling to try and start a religion vs atheism flame war. I trust no one is going to bite...
If you look through his posting history, it's a borderline troll account.

The bottom line is that we will forget 9/11/2001 as it too eventually sinks into the oblivion of distant history in the back pages of a book, eventually dwarfed by fresher and more shocking disasters to come.

Yes it will become insignificant compared to other disasters (and already is insignificant compared to the million Iraqi dead from '90-today), but will go down in history as the same kind of political event as the Reichstag fire -- there's been plenty of fires since, and it wasn't even that big of a fire at the time, but still it remains in the history books because it resulted in the loss of civil liberties, the granting of never-ending emergency powers, and eventually propelled a country into war.

edit: also, don't understand why the picture has a "Imagine no religion" text over it.

Depending on who you ask, the reason it occurred was simply because of religion. Nevermind that in the interview that's commonly cited as OBL's admission of being behind the 9/11 attacks (despite no direct admission appearing in the interview), he cites witnessing US bombing of Lebanese civilian apartment towers as the catalyst for his desire to destroy an American tower in retaliation, to shock their populace into denouncing their terroristic leadership. Didn't really work out for him.
Also, the radical islamist movement was non-violent, until a dictatorship tortured the soul out of their leader, convincing him that their enemies were too corrupted to be defeated with non-violence, and that they would have to fight fire with fire. Violence leads to violence. Image a world without violence...

The latter is a much smaller measurable impact, but is probably also more traumatic because of the impact it has on the perception of the safety of yourself and the people you care about.

I think pre-2001 Americans might have been unique in believing that they were somehow invulnerable.

Across the pond, we always lived with the knowledge that we might be bombed by the IRA, taken hostage by Basque separatists, or doused in gasoline and set on fire by PETA...

I just found a great troll post on another forum -- read carefully, and apologies to anyone offended by reposting the troll's work (having spoiled it already by pointing out it's trick):

Today is the anniversary of 9/11. I think we should all take a moment out of our time and remember the dead. That tuesday, without any provocations, the attacks happend. That day which has been engraved in our collective memory has changed the world completely. It's a day on which freedom and democracy itself was attacked. A cowardish attack, resulting in the deaths of 3000 innocent humans. Their lives lost, for no reason other than mindless, baseless hate. We should all work together to make sure such disgusting attacks never happen again.
In our thoughts today are the 3000 innocent deads, and the 130.000 innocents that were imprisoned and tortured.

We should never forget, and never forgive.

September 11, 1973.[/quote]

I just found a great troll post on another forum -- read carefully, and apologies to anyone offended by reposting the troll's work (having spoiled it already by pointing out it's trick):

Today is the anniversary of 9/11. I think we should all take a moment out of our time and remember the dead. That tuesday, without any provocations, the attacks happend. That day which has been engraved in our collective memory has changed the world completely. It's a day on which freedom and democracy itself was attacked. A cowardish attack, resulting in the deaths of 3000 innocent humans. Their lives lost, for no reason other than mindless, baseless hate. We should all work together to make sure such disgusting attacks never happen again.
In our thoughts today are the 3000 innocent deads, and the 130.000 innocents that were imprisoned and tortured.

We should never forget, and never forgive.

September 11, 1973.

[/quote]

Allthough it is worth remembering Sep 11 1973 aswell, it is a significant part of chile's history and there are lessons to be learned from it.