Juvederm in Glabellar Lines
you're right - injecting the glabella takes some skill and, if overdone, can lead to some complications. it is an area where the skin is not as well supplied with blood vessels as in other areas of the face.
if too much filler is injected, it can interfere with blood supply to the skin and some temporary redness swelling or even a skin infection. i had one case of this about 4 years ago and it taught me to be very conservative in this area.
however, if you choose an experienced injector and he or she is careful, you should get a great result. i use juvederm for this area - that way if there's any problem, i can dissolve the juvederm with an enzyme called hyaluronidase.