What is the validation sticker used for? I wanted to know because I dropped by McMaster a few days ago to get my student card and was informed that my validation sticker was on its way. However, I am moving in tomorrow and have still not received the sticker. What should I do?

I am pretty sure this problem happened to a lot of people last year so they knew to expect a fair number of people not to have them yet so it wasn't too much of a problem
The sticker just states that you are a registered student for the 2009-2010 School Year. Its mostly needed to use the buses. You could try to see if the registrars office will give you one, but I doubt it but you can try. I don't know why they mail them out so late. For three years mine was always delivered late so I had to get it mailed out to me. Last year they made out of province students pick it up at the Registrars Office.

It's also shows that you have access to the athletic centre. But technically you only have to scan the barcode to get in.