A make-up primer is good to use, especially when you're out for a night with your mates, drinking and having fun. You want to keep that look for the rest of the night, unless you want to look like you did your make-up when drunk (Ha, Jenna Marbles did that in a video...classic!)

However, it does have a downside. If you apply too much primer on your face where you aren't applying colour can detract the look that you wanted, mostly because primers typically are brighter in tone than most make-up shades :/