the problem with a concentrated approach. 
1. BP/Transocean - 2 seemingly invincible stocks and once overweighted  by all pension funds. 
2. Potash - the darling of value investors/monopoly/dividend
3. Gilead - the only cure hep-b and rock solid balance sheet with a strong pipeline of drugs

One could have easily concentrated their portfolio 10 years with the above stocks and be down 50% over that time, if not more.

To quote a line from The Glass Menagerie, "things somehow seem to have a way of going wrong".

Hold a balanced/diversified equity portfolio and investment grade corporate debt.