Mark 16:15 says, "and He said to them, 'go into all the world and preach the gospel to every creature'."
Colossians 1:23 says, "if indeed you continue in the faith, grounded and steadfast, and are not moved away from the hope of the gospel which you heard, which was preached to every creature under heaven, of which I, Paul, became a minister."
What do these two verses have in common? You probably picked up on the "every creature" phrase in each one, so let's think about that in depth a bit more.
Jesus's ministry would have likely concluded on this earth around 33AD, and it is post-resurrection that He issued the above command to go and preach to every creature. The book of Colossians was likely written between 64-66AD, so approximately 31 years later. Paul said in Colossians that the gospel had been preached to every creature in heaven already. So, in 31 years, the gospel reached everyone.
Now sure, there were probably less people on earth during that time. And sure, people probably weren't spread out quite like they are today. But think about it: there was less transportation, no technology, and yet every creature under heaven heard the gospel and all it took was approximately 31 years.
We have been given the same command that Jesus gave to the disciples in the first century: to go into all the world and preach the gospel. We were not told exactly how to go, just to go. So, we can still go and do face to face evanglism: there really is no better way! But, we can also use technology much like The Light Network is doing, and spread the gospel via the internet. We can use television programs, radio programs, Bible correspondence courses through the mail, and various other ways. But, in whatever ways we choose, we MUST 'go' and 'preach'.
Acts 8:4 says, "Therefore those who were scattered went everywhere preaching the word." It wasn't preachers and deacons and elders who went (though surely they were included in the number). Really, it was just Christians. As these Christians were scattered abroad, they taught--they were personal evangelists. In the same way, everywhere we go (overseas, cross-country, Wal-Mart) we must spread the gospel, and we must all do it. It wasn't a minority of first century Christians who spread the gospel, it was all of them! That's why they could accomplish such a great feat in 31 years.
If every Christian on earth right now would spread the gospel of Christ, imagine how quickly we could get to the entire world! Sadly, we cannot control every Christian. You know who we can control, though? Us. We can purpose to spend 2013 spreading the gospel of Christ to everyone around us. Will you please join me in this cause?
Jesus says it is those who love Him who keep His commandments (John 14:15). He has commanded we go. So I guess the only question left is, do we love Him?