As my home airport is YVR, and we do not receive much snow, this reminds me of an incident quite a few years ago. I was on an AC flight YVR to PEK and it was snowing a wet type of snow here in Vancouver. We went to the deicing station, got sprayed and as I looked at the wings, I thought there is still a lot of snow on them, but what do i know. Thinking that the crew and pilots knew what they were doing, we left to head to our take off runway. As we are on our way there, the pilot comes on the PA and announces that a passenger has informed the crew that there is still a lot of snow etc on the wings and we are now heading back to the deicing station. So if you see snow and ice on the wings, let the crew know as the pilots can barely see that and they are relying on the workers to do a proper job and I think some airports are just not that capable.