Remember: save your downloaded Lion installer before installations.
Euan Williams
While a lucky few have unlimited broadband and fast connections, people should remember that the Lion installer, when it becomes available from the appstore will, according to gold master recipients, wipe itself off your drive after Lion has been installed.Yes, it is supposed to leave a 'restore' version on a separate partition -- automatically, and this can presumably be cloned, and Yes, you can always download it again 'for free', but it may be wiser to use one or other known method to save the installer file to DVD and/or flash drive first. These methods are simple and easily followed.
Look under "The Roar of Lion" topic.