Facebook is a reminder that the simplest ideas are always the most valuable.

Or, as I tweeted earlier tonight:

Dumb ideas can be monetized better because the world is full of dumb people.

A whole lot about Facebook, looking at it even semi-objectively, is just plain dumb. Putting up a Facebook page instead of a website comprised of HTML, JavaScript, good design, database hooks, and rich media is dumb. That kitteh photo on your profile is dumb. FarmVille is dumb. A low-res photo service that badly degrades image quality is dumb. Advertising just so you can get more Likes, without a clear sense of how you make them customers, is dumb.

Facebook is dumb. And that is why it’s so brilliant.

In business, dumb is good. If dumb people can use your product, and even build stuff on it, that’s a good sign you have a $100 billion idea. There are lots more dumb people than smart people in the world, so the market opportunity of dumb is scarily vast.

The Photos product is the quintessential story of it not being about the technology, but instead keeping it simple and focusing on what really matters to people. Very early on, Facebook Photos overcame Flickr to become the largest photo destination on the web. That’s because it wasn’t about the photos themselves, but the people in the photos. The ability to tag, share, like mattered more than the ability to download a 4000×3000 copy of that gorgeous photo of a plant.

Facebook is killing HTML and killing the open web, but it doesn’t matter because the thing that really matters to people is not the web but socializing 24/7 with their real friends. Technology is secondary to simple human desire.

It’s not like Zuckerberg was the first to get this, either. Friendster tried. MySpace tried. Friendster couldn’t scale. MySpace sold out. Profiles and accounts tied to people — some real, some fake — were around since the earliest days of the web. That caveat turns out to have been a crucial limiter. When your friend list is polluted by even a small number of fakes, weirdos, or creeps, your trust in the network plunges to zero. I try every social product ever but I could never bring myself to use MySpace for this reason. I got up to about seven friends, and not only did I stop using it, but I deleted my account. Even seeing the email notifications that some bozo I didn’t know friended me was too much.

Zuckerberg solved this problem not by utopian social engineering but by rigging the game so people couldn’t play it any other way, limiting it first to harvard.edu addresses and then extending it to other college campuses. This did two things. First, it created a velvet rope effect where others clamored for access. And second it made it so that real identity was baked into Facebook from the very beginning. This is why people chose it over MySpace and why network effects were able to take hold.

In writing about the future of the Internet in recent days, I was reminded by how little intellectual property actually matters in this world, and how it’s really all about relentless execution and aligning the incentives with the desires of the user base. The most valuable ideas are the ones that are obvious and universal: Searching for things online, social connections, frictionless communication.

The next $100 billion idea will be the really obvious thing no one has done yet.

And, yes, finding that thing is about as impossible as it sounds.