The way around this is to use a mouseover handler on a "clickable element", as Apple explain in their Web Content Guide:
Mouse events are delivered in the same
order you'd expect in other web
browsers [...]. If
the user taps a nonclickable element,
no events are generated. If the user
taps a clickable element, events
arrive in this order: mouseover,
mousemove, mousedown, mouseup, and
click. The mouseout event occurs only
if the user taps on another clickable
item. Also, if the contents of the
page changes on the mousemove event,
no subsequent events in the sequence
are sent. This behavior allows the
user to tap in the new content.
Tapping once on a clickable element that has mouseover/mousemove content displays that content. Tapping a second time does mousedown/mouseup/click.
A "clickable element" is:
a link, form element, image map area,
or any other element with mousemove,
mousedown, mouseup, or onclick
(Apple has patent applications for detecting hovering on touch interfaces, so this could go away in the future. However, it's unlikely that will be soon).