After years of separation, investors have finally rekindled their love affair with stocks. That on-again, off-again romance is definitely back on again, with billions going back into stock funds each month. Investors' infatuation with bond funds is also ending. Nearly $100 billion have come out of bond funds in 2013. They're just not that enticing anymore. Does this mean we should expect trouble down the road for the stock market, and if so, what sort?