Well, it shows here (using wmctrl 1.07)
[alexandernst@stupidbox ~ 20:37:24]$ wmctrl -l
0x01e00234 -1 stupidbox plasma-desktop
0x01e0023d -1 stupidbox plasma-desktop
0x01e00222 -1 stupidbox plasma-desktop
0x01e0022b -1 stupidbox plasma-desktop
0x00c000c5 0 stupidbox aMSN + wmctrl - Mozilla Firefox
0x0280001c 0 stupidbox KaKaRoTo – Konversation
0x02a0001b -1 stupidbox Yakuake
0x0340000c 0 N/A aMSN - alexandernst@gmail.com
[alexandernst@stupidbox ~ 20:37:34]$