http://getsatisfaction.com/mozilla/topics/keep_ubiquity_window_opened_when_change_focus

noautohide.ubiq.js

function cmd_toggle_autohide(){
  displayMessage(toggleAutoHide(context.chromeWindow.gUbiquity), this);
}
function toggleAutoHide(U){
  var p = U.msgPanel, nah = noAutoHide(p), b = nah !== 'on';
  p.setAttribute('noautohide', b);
  p[(b ? 'add' : 'remove') +'EventListener']('keydown', manualHide, false);
  return nah;
}
function noAutoHide(p){
  return p.getAttribute('noautohide') === 'true' ? 'on' : 'off';
}
function manualHide(e){
  if(e.keyCode !== e.DOM_VK_ESCAPE) return;
  e.preventDefault();
  e.stopPropagation();
  this.hidePopup();
}

CmdUtils.onUbiquityLoad(toggleAutoHide);

$.extend(cmd_toggle_autohide, {
  icon: 'chrome://ubiquity/skin/icons/favicon.ico',
  author: 'satyr', license: 'MIT',
}).__defineGetter__('description', function tah_desc(){
  var U = (context.chromeWindow || Utils.currentChromeWindow).gUbiquity;
  return ((U ? 'Turns '+ noAutoHide(U.msgPanel).bold() : 'Toggles') +
          " the auto-hiding behavior of Ubiquity panel.");
});