Having inside-depth knowledge nor references, I do not think the opening scene is intended to be humorous. To my opinion, the opening sequence serves foremost as an introduction to Mark's character and his intelligence, but at secundarysecondary level as a preview to the audience to what is be expected, namely the rapid pace of conversation and mind-switching. It is saying: "Pay attention!"
Some people label parts of it as being humorous, but that is just individual taste. This scenescene's calling up of different emotions is evidence of Aaron Sorkin's superb writing.