jan@xylakant:~$ lsb_release -rd
Description:	Ubuntu 10.04.2 LTS
Release:	10.04
jan@xylakant:~$ apt-cache policy nautilus
nautilus:
  Installiert: 1:2.30.1-0ubuntu1.1
  Kandidat: 1:2.30.1-0ubuntu1.1
  Versions-Tabelle:
 *** 1:2.30.1-0ubuntu1.1 0
        500 http://de.archive.ubuntu.com/ubuntu/ lucid-updates/main Packages
        100 /var/lib/dpkg/status
     1:2.30.0-0ubuntu4 0
        500 http://de.archive.ubuntu.com/ubuntu/ lucid/main Packages

I've mounted a partition and a directory of this partition via bind, i.e. in /etc/fstab:
/dev/sda7   /media/data   ext4   defaults   0   0
/media/data/downloads   /home/user/downloads   none   bind   0   0

If I move files to trash in /media/data/downloads, they are moved to /media/data/.Trash-1000 and are shown in the nautilus trash bin.

If I move files to trash in /home/user/downloads (what is the case almost any time), they are moved to /home/user/downloads/.Trash-1000 and are *not* shown in the nautilus trash bin.

This could lead to a hard drive spammed by trashed files not seen by nautilus and should be regarded as a non desired behaviour unlike stated in a similiar bug report concerning a slightly other situation (https://bugzilla.gnome.org/show_bug.cgi?id=604015). BTW thunar can handle this (i.e. it sees all the files moved to trash via nautilus).