For all of those designers who haven't noticed, the reflection is the new design craze. With Mac using it all over there site, you start to hundreds of other sites following along. Even though I think it looks nice and have used it myself, it will probably get old really fast and become as the drop shadow, which you should hardly ever use. But like the drop shadow, if you can use it so it is not distracting, then no harm done.
If you are interested in having this effect, there are many photoshop tutorials that can explain it to you or there is even javascript that will achieve the same effect.
Also note that everything on your website doesn't need to have a reflection on it. Use it on items that you are highlighting or that you want to draw attention to. It's all about heirarchy and where you want your visitors eyes to go.