I don't think Square was overvalued at IPO. As for today's drop: the fall in oil has hit everyone, unfortunately Square's fall of around 8% is worse than most. For Example today AMZN saw a drop of around 4% and TSLA is down 5.5%.
Don't be wary ;)
Don't be wary ;)
When the price of oil falls, that indicates that people are pulling back on oil/gas/etc purchases due to constrained budgets, reduced business/operations, etc. (and/or that people buying the oil predict that others will cut back on those things in the near future)