Agree with you on diversification across sectors. Why split your capital across say 10 stocks in 10 different sectors, so that the hot sectors balance out and hopefully reward you against the cold sectors, when instead you could put all your capital in a hot sector? To guard against risk, instead diversify across a few companies in the hot sector. If you follow the market closely, it should be fairly obvious if a hot sector starts to go off the boil.
Regardless, you should be picking what you consider are "hot stocks" anyway, whatever the sector.
