Actually, Riedel claims purposefully to makes their bubbly stems with a rough patch at the bottom of the interior crystal to induce better streams of bubbles. Eric ← that, and crystal is rougher textured then glass, too, which is why it's more suitable for wine in general. The rougher texture creates a sort of micro-aeration of the wine, furthering the release of the bouquet. ← If you haven't tried them yet, the crystal stemware from Eisch is very cool. The micro-texture in them is enhanced to allow a further immediate oxidation in the wine. I was skeptical, but after trying them out, I was convinced. Google them for comments from Parker, Tanzer and such.