Laser technology has become very safe. As recently as the year 2000, we could not treat patients with darker skin. They were not candidates for laser hair removal, no down time skin rejuvenation, laser vein removal etc. Now they are.
The most important thing that determines your risk of complications is the setting where your laser treatment is performed. Were you properly evaluated by a physician? Were you seen by a board certified plastic surgeon? There are many different doctors out there (most of whom are not plastic surgeons!) that are offering laser treatments. What's worse is that they really do not get involved much with their patients - even after they have a complication.
The complications vary depending on the type of laser and what is being treated. The one complication everyone worries about is burning a patient, which usually leads to a scar! The risk overall for most procedures is about 1-2%. It does happen. There are many things that can be done to decrease its occurrence. Make sure you see a board certified plastic surgeon. Remember, their training specifically deals with cosmetic surgery. The training is at least 6 years after medical school!
One more thing to think about. When dealing with a small burn or complication, plastic surgeons are in a very good position to deal with this issue. After all, who do you think treats burn patients?? To us, a burn is easy to deal with. To non-plastic surgeons dipping into the laser market, it is a big problem.
A few examples of patients burned by the laser (elsewhere)...