Flash could make a battery go in a flash.
When Apple shipped its latest MacBook Air laptops without Flash preinstalled, it gave the explanation that it would rather users installed Flash themselves so that they could get the latest, most secure version.
This is a plausible explanation because often times Apple fails to include the latest build of Flash even in its most recent Mac OS X updates. The latest builds of Flash include GPU video acceleration – something that current Mac users have to upgrade themselves if they want the feature.
There could be another very big reason that Apple left out Flash in its latest, thinnest laptops, and that would be battery life.
In Ars Technica's tests of the 11-inch model, it found that the little laptop survived 4 hours of Safari web browsing with Flash enabled. With Flash taken out of the system, the laptop ran for just over 6 hours.
Apple quotes a 5 hour battery life for this particular MacBook Air, so real world numbers appear to be within a close range of that. Still, for those on the go with a new MacBook Air, is it worth sacrificing a third of your battery life for Flash?
Perhaps the best solution would be to have Flash disabled elements until the user decides to display them, like Click to Flash.