Dramatically declining PC sales have caused major stock-price declines for companies that are linked to the sector, such as Intel ( INTC) and Microsoft ( MSFT). Everywhere you look, EPS estimates seem to be under assault. Heading into first-quarter 2013 earnings season, negative pre-announcements were at their highest levels since those statistics have been kept. The S&P 500 has already experienced two straight quarters of year-over-year EPS contraction. A third-consecutive year-over-year decline would likely cause concern in some quarters that earnings have peaked and that this will signal a top in stock prices for this particular cycle.