Fundamental changes will first have to be made in the poorest parts of the world to deliver on Internet.org, as his project is named.
"I'm a believer in the power of connectivity even at the bottom of the pyramid, but I don't know if the ambition of connecting 5 billion people is realistic when you consider the fundamental challenges facing it," said David Rice, professor at New York University and Africa adviser to the Milken Institute.
There are four main issues: The shortage of electricity throughout the developing world, a lack of broadband infrastructure, extreme poverty and widespread illiteracy.
Here's the good news: Most of the world's population has access to one basic form of communication: cell phones and text messaging. That's made possible with an abundance of cell towers throughout Africa.
But phones that connect to the Internet require a lot of electricity. And 60% of Africans have limited access to it, according to Rice.
Just to charge their phones, some people drive hundreds of miles into the nearest city or tap their car batteries for some extra juice. The problem has created a booming market for solar-powered charging stations. But the businesses that run them typically charge exorbitant fees.
If these phones were suddenly connecting to Facebook, ( that's going to drain the battery a lot faster than placing calls and sending texts. )
The second issue is the lack of broadband infrastructure. Sending calls over cell towers is one thing, but tapping into all the data on the Internet usually depends on fiber cable.
It would be prohibitively expensive to wire remote villages. That means cell towers in remote areas would have to carry the load. But they could easily be overwhelmed with traffic if people were suddenly using their phones to connect to the Internet.
One of the pillars of Zuckerberg's "rough plan" is to make mobile applications more data-efficient so they suck less precious bandwidth.
The connectivity problem is one that local governments and Western Internet companies have sought solutions for over the past several years.
In unconnected places, people sometimes get temporary Internet access from roving satellite-connected Wi-Fi hotspots on the back of donkeys or buses. Villagers will wait for the Wi-Fi hotspot to come to town, and they'll gather around to quickly check e-mail or browse the Web.
Other companies are also trying to crack this problem.
Google (Fortune 500) is sending balloons with radio antennas into the stratosphere as part of a project called "Loon." ,
Alcatel-Lucent ( is bringing its inexpensive lightRadio technology to small villages without cell towers. )
And phone manufacturers are racing to develop smartphones that cost less than $15 -- a goal that even top-tier smartphone makers such as Nokia (, Samsung and )BlackBerry ( are working on. )
There are others issues too. To get the benefits from Internet access, developing countries must tackle the widespread illiteracy that persists. If people can't read and write, then email, Facebook and other text-based communications apps will be worthless.
Impoverished people also tend to buy very rudimentary phones that are capable of texting and calling -- but not much else. Phones that are able to connect to the Internet could easily price many people out of the market.
And some worry that the path to full access will only exacerbate that problem.
"It's easy to be cynical about this Internet.org stuff," said Keith Proctor, fellow at Tufts University's Feinstein International Center. "If they can't address the issues of cost, power and illiteracy, there's a danger they'll just end up entrenching those inequalities."
Despite the challenges, Zuckerberg's vision is admirable. "They're going to use it to decide what kind of government they want, get access to health care for the first time ever," he told CNN. "Connectivity is a human right."
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