Please help on a *very* basic usage

Hi,

I installed notify-send, which comes in standard distributions under
the package "libnotify". I can use it easily:
$ notify-send "hello world"
pops up "hello world" in a nice notification bubble.

Now I try to use it with notify-send:
$ incrontab -e
/home/me/foo IN_CLOSE_WRITE notify-send "foo has been modified."
$ touch /home/me/foo
nothing happens. Why? (trying to export DISPLAY=:0.0 doesn't work)
Received on Tue Jun 05 2012 - 22:14:21 CEST