We've used <i> for icons before. Main reason we started doing it, I seem to recall, was that we needed some sort of element there to make the spritesheeting wor

We've used <i> for icons before. Main reason we started doing it, I seem to recall, was that we needed some sort of element there to make the spritesheeting work easily, and a lone empty <i> is (a) short, (b) extremely devoid of meaning which might be added to it by browsers/readers, and (c) easy to remember when writing markup as i-for-icon.