I always figured blind fire being shooting around a corner without taking yourself around said corner... definately a perfect setup for serious accidents...
Shooting above bunkers like in the first picture is also a bit dangerous and still goes into my blind fire category, as someone might just have crawled up to there and stand up to surprise you (sadly, with an upgraded rifle cranking BB's up his face to no end)
As for shooting without using the sights, that's just a different way to handle your weapon, if you can aim well without using the sights, good for you. At best, it gives more survival chances to the ennemy
I've shot from the hip alot back in the days, considering I could not use the sights of my rifle, but I always kept my eyes on where my gun was pointed when the trigger was being pulled. I also noticed that my kill/BB ratio went way up once I got a scope mount and a low-mag scope on the rifle.
Using black BB's sure didn't help me track down their flight paths, but it sure kept the targets from dodging the BB's!