The single biggest mistake I see with strength coaches and trainers is turning everything into a numbers game and neglecting technique and muscle function.
Strength coaches often feel overly compelled to increase the numbers and weights their athletes are using simply as a way to display to the athletes and coaching staff that their training is producing results.
Although this may produce a quick yet temporary increase in numbers, unfortunately it leads to dysfunctional movement patterns, injuries and training plateaus.
One method I see used consistently in weight rooms and gym settings that encourages this problem is the use of what I refer to as "assisted spotting."
In essence, the trainer or strength coach spots the athletes by actually helping them lift the weight, since excessively heavy loads are greater than what the athletes are capable of handling.
It's very common on the Bench Press as well as the Squat.
It is often done to increase morale and ego of the athletes; however it does little to stimulate strength and size gains.