Paul Hiebert examines it:
In a sense, when a teenager deems a person or idea "So random!", they are being dismissive of that person or idea. The teen who utters this word after being confronted with something unfamiliaran event that doesn't resonate with his understanding of the universeis in a way regaining control by restoring order. What is random is folly, and therefore not a threat. In other words, it's comforting to consider our beliefs and perspectives as logicalthey make sense, after allwhile any beliefs or perspectives outside of, or in opposition to our own, must therefore be chaotic, confusing, random.