Not restarting this thread for the sake of it, but for anyone else looking for this same topic, it's worth replacing it if it comes off. Mine was loose and had been zip-tied multiple times, but a long trip and some bad weather broke both front fixings, I now have a coolant leak I've hopefully fixed with Radweld (presumably something from the road or guard flew up and smacked the radiator). I pulled over, switched the engine off whilst checking, and it wouldn't restart, presumably the fan going mental at the coolant loss had killed the battery off, admittedly it was the original from '09 so done pretty well, but up until that point was still putting out a healthy 13v voltage. Immediate cost was over £100 for the AA to replace battery and chuck some coolant in - he also removed the guard entirely.
Few days later, we've had torrential rain and after hitting some big puddles had the 'Check Engine' light come on, with some heavy shuddering and low power - thankfully it seems to have dried out and was fine later the same day so I presume water got into a sensor, but it's stress and expense that can be avoided. I might go for a steel cover in the hope it has more ground clearance than the stock one. We have those horrible 'middle of the road' speed bumps around here and it's really just a matter of time before one catches my sump tank a good'un.