To me, using bad technique is like trying to build a house with only a bulldozer. At some point, you either aren't going to be able to build anymore because your foundation/equipment are too limited, or the whole thing is going to come crashing down. A foundation needs to be laid properly or you won't be able to get anywhere.
And in response to a poster above me, SOMETIMES "good technique" is the form that allows you to lift the most weight - in the case of something like a deadlift. But in bodybuilding, this is not true for everything or even most things for that matter. The form that allows you to squat or bench press the most weight is unlikely to be ideal for building your quads or pecs, in my opinion.
Exercises should always be forceful, but performed deliberately and smoothly, with as much focus and concentration on the stretch and contraction of the target muscle group as possible.