Are bubble charts effective? This seems to be a recurring question. Some say people suck at comparing areas in the form of bubbles, or rather, people are horrible with areas, period. Others argue that it just takes some getting used to; the eye has to be trained, and once that's done, the bubbles are good to go.
In any case, here is an alternative to the bubbles -- bars. The beer data from a previous post are charted (2006 shipments on the left, and 2005 shipments on the right). The advantage of bars over bubbles is that users only have to compare heights; however, numbers are going to clutter quickly as more observations are added.
People should just train their eyes. Bubbles are so much more fun. They're bubbly.