The 4% drop isn't catastrophic, but the timing's awkward. Investors like to end the week in a stable position, and historically the Friday after a Thursday drop has seen an even bigger drop as investors dump whatever they're not sure is solid.

Something weird happened to Procter and Gamble today, losing fully half their value (but recovering somewhat later), and everybody's still scratching their heads to figure out that one. It probably had as strong an influence on today's selloff as the Greek problem. Speculation is that there might have been a glitch in some computerized trading software, and the "sell baby sell!" bit got stuck on.

The stock market's been way out ahead of the rest of the recovery. To put it bluntly, capitalists are doing fine, but workers are still hurting. The drop could also be seen as a correction that brings Planet WallStreet back closer in touch with reality here on Earth.