Momentum vs. Buy and Hold

Two investment strategies.  Some validity to both.  Momentum tries to identify which stocks will go up the most.  Buy and hold tries to identify good companies that are underpriced.  I'm a fan of buy and hold.

To be a smart momentum investor, you must sell a stock when it becomes massively over-valued.  For instance, you'd want to sell Netflix or Facebook right now after buying them when they were super low.  But buying stocks this way means you incur transaction fees and must pay taxes on the gains.  Plus, you need to find somewhere else to park the money, thus incurring more transaction fees.

With a buy and hold strategy, you don't need to sell if the prices get too high, but rather be on the lookout for a systemic problem with the company itself.