Similarly to RSI, the MACD simply doesn't work. Well to be totally fair, the RSI does work in very rare instances but you really have to know what you are doing and have a very specific strategy set in mind.
Oscillators like MACD and RSI are particularly weak indicators because they can't distinguish between range and trend, so following them alone is often a death trap. However, if you use multiple approaches (like candlestick, volume, and MA analysis) in addition to oscillators and look for confluences of bullish/bearish signals, they can be useful at times.
No single indicator should be followed on its own.