By Blekko’s own analytics, the number of unique IPs it saw went from 1.58 million in December to 5.33 million as of the beginning of this week. Looking at their chart, the biggest spikes seem to have happened between December and January, when the search engine nearly doubled its traffic, and between March and April, when it went from 3.71 million unique visitors to 5.33 million unique visitors so far this month. Matt McGee notes that this represents a 337 percent rise in visitors just in this year – and April isn’t over yet. The year-over-year numbers are similarly impressive. McGee compared…