Even a very good stock can plunge your portfolio. Buy and hold strategy is as same dangerous as other strategies.
I personally am against such strategy. During bear markets or some disastrous events you may end up with a huge loss without recovery.
I advocate an active portfolio management, using stop loss and protect my portfolio against downtrends. Some stocks may make you money over a long haul, some can lose you money over that period and it can be a good stock which can turn into a bad one within a day.
Read this what "buy and hold" strategy can do: