Principal Component Analysis

In PCA the first dimension of the basis vector has the highest variance and the last has the least variance.

So if we are using PCA just for dimension reduction why cant we find the variance of individual features, sort the features in the descending order of the variance and just use the first n features/dimensions.

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What do you call the "features" ? – Stéphane Laurent Oct 3 '12 at 7:20
stats.stackexchange.com exists... – Gottfried Helms Oct 3 '12 at 7:47