Depends on life goals. If your primary goal is to amass further wealth, large bets on single items/industries can pay off very well. However, if your goal is to not lose wealth, then diversification is a very good strategy. The OP is in the latter school with these particular investments.
Additionally, I find it ironic you bring up Buffett: Berkshire is diversifying out of insurance :D
>Foremost, though, was his acknowledgment of the need for Berkshire to expand its non-insurance businesses, a broad collection that most prominently includes the railroad Burlington Northern and the electric utility MidAmerican.
Expanding on your advice: when diversifying it helps to not throw darts. It may be best to not have investments only in tech, auto, health, etc., but it's quite another to randomly choose a company or two in different sectors.
Unsolicited advice ;-):
* Tech: ARMH over MSFT over FB (phones/tablets need to be low, low power and P/E of FB seems egregious)
* Auto: VLKAY over F over GM (100MPG TDI trumps "made in USA" trumps bankruptcy)
Additionally, I find it ironic you bring up Buffett: Berkshire is diversifying out of insurance :D
http://www.financialexpress.com/news/warren-buffett-scouts-f...
>Foremost, though, was his acknowledgment of the need for Berkshire to expand its non-insurance businesses, a broad collection that most prominently includes the railroad Burlington Northern and the electric utility MidAmerican.