When I first started out lifting and didn't really know what I was doing I was helped out considerably by random people in the gym advising me on form and technique. I never minded people pointing out my shortcomings and actually thanked people for saving me a lot of time and effort doing exercises wrong. Now I know what I'm doing though, I never point out to others in the gym who have particularly poor form unless I think there's a chance of injuring themselves. The few times I did do it, my advice was met with awkwardness from people who clearly rather continue to waste their time than face the embarrassment of being told you're doing something wrong. So when you see beginners struggling away with poor form lifting as heavy a weight as they can do you advise them, or do you just let them do their thing?