The issue isn't Flex, but the Flash Player. It is too much of
a security risk to allow SWFs running in the Flash Player to open
local files. Imagine going to a web site that has a SWF banner ad -
but that banner ad opens local files and sends them to a remote
system - all of your personal and financial information transfered
without your consent.
Flex apps running in the AIR player are different - the end
user must launch them explicitly, just like any other local