This is exactly why I despise most Ajax implementations.

Everyone uses their Back button a lot — 95% of all Firefox users clicked the Back button in the 5-day test period, and it’s the second most-used button on the entire UI (behind the Location Bar). I thought more people had back buttons on their mouse; obviously not! Backspace on the keyboard works most of the time too…

via Mozilla releases interactive Firefox heat map illustrating just how often we hit the back button.