The rally in Apple has “had some unexpected effects that investors should be aware of: chief among them is the risk of overconcentration, as a great many indices and the ETFs that track them are weighted by market cap,” writes Dave Fry at ETF Digest.

Some sector ETFs use equal-weighted strategies to avoid concentration in individual tech stocks. They include First Trust Nasdaq 100 Equal Weighted Index Fund (NasdaqGM: QQEW) and Guggenheim S&P 500 Equal Weight Technology (NYSEArca: RYT).

PowerShares QQQ