jrb mentioned to me today that some users ssh -Y to remote machines then forward xterm to the local machine so they have a shell to easily launch remote apps from.  Each forwarded xterm ends up showing up as a separate icon in the dash.

This is because of this code in shell-window-tracker.c, I think:

get_app_for_window (...)
{
...
if (meta_window_is_remote (window))
  return _shell_app_new_for_window (window);
...
}

That is to say all remote windows get assigned their own fake app instance independent of others, and that app instance isn't matched to any particular desktop file. It's interesting because lower in the get_app_for_window function a comment notes that doing _shell_app_new_for_window() is a last resort in the local case.  So I guess it should be a last resort in the remote case as well.

I think a better behavior would be to:

1) match the wmclass of remote windows against locally available desktop files so it gets the right icon etc (assuming there's a desktop file locally that matches)
2) assign all windows for a given remote host and wmclass to the same app (which would be a different app than the local instances)
3) include in the dash icon tooltip the hostname (just as the hostnames are included in the titlebar)