Despite prohibitive costs and severe restrictions, cellphone usage in North Korea is rapidly accelerating, with Reuters reporting that one million phones are expected to be active by the end of 2011. While that doesn't seem like much, it's important to note that cellphones were banned completely from 2004 to 2008, and that two years ago there were only 70,000 active cellphones in North Korea. This restriction came after a 2004 railway explosion was suspected to be detonated by a cellphone — this explosion happened just hours after North Korean leader Kim Jong-il had passed through on the same train line.
Since the ban was lifted, most users are concentrated in the capital city of Pyongyang, where the greatest concentration of wealthy elite are located — and you need to be in that elite to afford a cellphone. According to Reuters, a phone costs about $350, while the average monthly income is $15. Despite the cost, functionality is limited: calling into and out of North Korea is not allowed (a citizen was executed last year for calling South Korea), and internet usage is completely blocked as well. Due to these restrictions, there's little concern from the government about mobile phones playing a role in an uprising (similar to what's been seen in Egypt). The average North Korean citizen is still a long way from owning an iPhone.