It's an interesting question. You might dismissively answer that Zuck just "got lucky" - but in doing so you'd be missing the opportunity to understand what makes a successful entrepreneur. In fact, a psychologist might say that those choosing to believe "he got lucky" are actually just trying to protect their own egos, to avoid acknowledging their own limitations. Namely that a 19-year old with few formal qualifications was not just more technically-savvy than the millions of us who call ourselves technologists, but also more business-savvy than the millions who consider themselves businessmen.
So why didn't you, or I, with all our educational advantages and years of professional experience create Facebook? Here's 10 reasons to ponder:
1 We weren't hungry enough
By the time Zuck sat down to write Facebook in 2004, I was already a start-up veteran. I'd been the fifth employee in a pioneering London dotcom, helping to build and run the company's services platform. But I became worn out, and by 2003 I'd left to go travelling for 5 months, which proved to be an awesome adventure - so much so that when I returned to work, my plan was simply to earn enough go travelling again. At this point in my life, I didn't want to change the world, I wanted to see the world.
2 We weren't itchy enough
Most successful ventures start because their founders have an itch they need to scratch, before realising that other folks also have the same problem, and there might be a business in providing a solution. For Zuck, the itch was how to connect with fellow students better (and a Napsteresque desire to share news and music throughout a dorm). Once he realised there was a demand for an online version of the paper 'face books' his college printed, he went ahead and built one. What's bothering you today?
3 We weren't visionary enough
Almost everyone's first online experience is having a conversation. Networks are inherently social, that's obvious, we use them to talk to others. Nevertheless, it wasn't until Facebook arrived in the UK that I started to understand Social Networking, and its distinguishing feature: on the internet you can talk to anybody, but on a social network it's just your friends. As a consequence, the services you build upon a social network are specialised: to share the stuff that binds you together. If I'd asked you in 2004 to draw the internet in 2010, would it have looked anything like this?
4 We weren't courageous enough
There are two ways to work in a startup: found one yourself, or join the team at an existing venture. For the past decade, I've done the latter; eschewing the harder, riskier and more stressful path of the founder, for the slightly less stressful role of senior techie. You have to be very driven to consider swapping the security and rewards of a job you've worked so hard to achieve for the uncertainty of founding something new, which might not even work.
5 We weren't connected enough
In our hubris, it's easy to over-estimate what we can achieve on our own. But eventually life teaches us that who you know is indeed just as important as what you know. What's a better investment? Spending 1000 hours reading everything about this year's hottest new technologies, or spending 1000 hours attracting an awesomely-connected mentor like Sean Parker? These days being connected doesn't mean you have WiFi, it means you have access to the kind of influential people who can help you change your world.
6 We weren't located well enough
What have Apple, HP, Oracle, Sun, Yahoo, Google, Facebook and Twitter all have in common? They all grew up in the same small corner of California. (And here's the reasons why). Such is the area's cachet, even the 6 month old Facebook moved from Boston (no high-tech wilderness) to Palo Alto, to be better connected. I suppose I could have moved there too, but chose to stay near my friends in London, where the startup and VC community is smaller and much less vibrant.
7 We weren't skilled enough
Or perhaps more accurately: we lack the right balance of skills. You might be an expert at designing and implementing software, but how much do you know about incorporating a company, or contract law, or tax allowances, or sales and marketing? I came away from university knowing all about how computer systems work - from low-level memory registers right up to complex artificial intelligence applications, but next to nothing about how to build up businesses. Then in the years subsequently, I kept on deepening my technical knowledge. Perhaps the moral here is avoid specialising too deeply, and instead look to broaden your horizons, and become a creative generalist instead.
8 We weren't adventurous enough
Being an entrepreneur is more difficult than being an explorer, because there is no map to guide you, and the blank spaces aren't visible until you stumble across them. Say, in 2005, you were inspired to follow in the footsteps of Facebook - would you attempt to compete for the same niche or try to pioneer something new? Would you have spotted the possibilities of a brand new niche for a real-time web-scale bridging network? Twitter found that one. As Steve Blank says: companies execute business models, startups search for new ones. There's always another blank space to find, if you're adventurous enough.
9 We weren't determined enough
There is a passion in creative artists that makes them strive to create new works, because creating things is their calling. As Paul Graham says "the most important predictor of success is determination". But I have been content to earn rather than yearn, deploying my skills to further others' projects, and being well paid for doing so. This is just how the world works, the determined few hire the talented many to make their visions happen. Are you sitting comfortably?
10 We weren't motivated enough
A quick straw poll of friends reveals virtually everyone has their own pet idea or hobby project, but few are actively considering turning it into a business. So those ideas will be left to marinate inside their heads, until someone more driven comes up with the same idea, and goes that bit further: filling in the company paperwork and putting in the late nights. Ever noticed there's a lot more late night hacking in 'The Social Network' movie than soliloquies? The real pioneers just do it.
So the reason why I didn't create Facebook has little to do with personal characteristics, otherwise I might as well have written an article called "10 reasons why Usain Bolt runs faster than me". Instead, the reason neither of us created Facebook is a result of where we've come from, our attitudes, and - crucially - the life decisions we've made along the way. Most people, me included, tend to choose the comfortable path. Perhaps that's why our culture respects entrepreneurs highly, because in our comfy, cosseted modern life, they're amongst the rare few willing to leave their comfort zones to actively seek out new struggles.
So whilst the opportunity to build Facebook is past, new opportunities still lurk undiscovered in the blank spaces, awaiting the determined and the adventurous. Perhaps you already have all the skills you need, perhaps you don't need any.
And that's why I didn't create Facebook. What about you?