The answer is yes, but exactly how much and whether it's bad is debatable. Glass has a bad reputation among some audiophiles. You'll find comments about ringing and glass adding a hardness to the sound of components. In the past I've used glass and didn't have any problems, but I was using fairly thick 1/2 inch slabs. If you want to experiment I would suggest starting with rubber or cork type footers to see if you notice an improvements in sound quality.
Do glass shelves affect sound Quality?
I have a TV cabinet with glass shelves that houses my hifi components. I'm wondering if the glass shelves could affect the sound quality of my components. I have a Classe pre/pro and 5 channel amp, Oppo 95 player and the Olive 04HD.