What would happen if one were to do this due to the fact that this person has a hard time finding veins in any other places.

just my guess.

once wouldnt be too harmful but dont do it more than that because i dunno about you but i could handle needle-related diseases in my arm but in my dick....

I knew someone who did this fairly frequently but I'm not sure of his exact technique and keep in mind this was someone who had been using heroin for about 20 years.

It's not unheard of.

lol dude even if you have trouble, have a little pioneer in your spirit. i look at spots that i can't hit anymore that had veins there and move north/south of that spot keepingin track with where the vein should be, i always find my target.

Nothing really wrong, but be extra careful, you dont want to get an infection or collapse a vein.