Every plastic procedure has risks. These can be minimized by going to a board certified plastic surgeon who has experience with this technique.

Doctors take significant time to discuss risks, benefits and alternatives to surgery. Risks include the same risks with liposuction (the more common ones are contour abnormalities, asymmetry, bruising and infections - those these are all relatively rare).  Additional risks include failure of fat to take (typically about 10-20% of the fat injected does not survive).

I hope this helps!