I haven't had any hypo awareness for at least 10 years now and the risks are considerable. As mo says there is the possibility of coma or worse. I started going unconscious without any warning, you lose any early warning signs that your blood glucose is dangerously low and feel normal until you go so low that you start fitting and pass out. It is very frightening to cope with as you don't know when or where it might happen, putting you at risk of physical injury. I am constantly checking to see if I am at a safe level.
I'm very fortunate to use a continuous glucose monitor that sends an alarm to my pump to warn me when my levels are falling too low and this can also automatically suspend insulin delivery to my pump if my levels continue to fall. This is a life saver especially at night when my most frequent hypos occur.