I herniated my lumbar disc doing deadlifts.
I had perfect form for 5 years straight, and one day I was tired and messed up my form, and BAM! herniation!
This, IMO is a hugely dangerous lift and had I known back then I would have never done it. I rather have a weak back than risk becoming a paraplegic.
Like many things in life, its not dangerous in and of itself, its the user that causes the problem. You said so yourself, YOU messed up your form! The lift didnt cause the damage, YOU did.
Anytime you are lifting weights you should make sure your in the proper mindset and health to do so. That being said you should have your form observed and critiqued by someone who KNOWS what they are doing and your form should be spot on before attempting anything near 1RM. Even with that being said you should in no way sacrifice form for weight during normal training.
Take video and along with coaching and know what breaking form feels like and when it occurs drop the bar. You have nothing to gain and everything to lose by squeaking out a rep with poor form.
The above being said, the DL causes system wide benefits that no other exercise can match. There sheer stress it imposes on your system causes massive CNS and muscular adaptions, large spikes in natural hormones etc which all equal growth.
For those that want to scoff at DL's and push them aside as dangerous or unneeded thats your choice but personally I want to be able to know that if needed I can pull 600lbs off the floor in an emergency without becoming a cripple.