After reading through these, I think whether it is ethical or not depends on the approach and timing. "Ambulance chasers" are on the scene in a very short time and in person, which means they are dealing with people potentially still in shock or in a fragile state of mind. Plus, since they are in person, it could be much more aggressive.
But reading Stephani's post, I personally don't see that as unethical. A postcard is not going to force someone to do something they will regret, and it came later than the actual event, which allows everybody to calm down and regain their senses. All it did was allow her to identify the specific pain point and offer a solution. I think that is good marketing and good service all around.