Do you use IBM Sametime in KDE and wonder why it won't open your chosen file manager when someone transfers a file to you? Well, the Sametime team uses an Eclipse call to gvfs, rather than (what I thought) xdg. The KDE control panel configures xdg, so now I know why Sametime is ignoring it.
To get Sametime to open Konqueror, for example, use this command:
gvfs-mime --set inode/directory kde4-kfmclient_dir.desktop
Tags: 
kde
sametime
file