I've used that line often, too - but you have to follow up with something that is your real opener.
Just asking for a light is not an opener, in my opinion. But it does allow you to gauge her interest (if she smiles at you, looks at you, etc.) and then deliver the real opener, or just say thanks for the light and eject.
Just asking for a light is not an opener, in my opinion. But it does allow you to gauge her interest (if she smiles at you, looks at you, etc.) and then deliver the real opener, or just say thanks for the light and eject.