The first risk involves the surgeon. For a proper procedure, the cosmetic surgeon must be a good one. You have a lot to lose if he turns out to be bad at his job, or relatively inexperienced.
The second risk has to do with the procedure. You do not know, until the operation is over, that things have gone well. Sometimes by the time you know, it can be late. Rectifying a botched cosmetic surgery is a long and painful process.
The third risk is the money factor. Cosmetic surgery itself is a costly affair. Having to spend more because of the surgeon's inefficiency can be irritating and frustrating. Of course, in the event things go wrong, you can always claim damages, but that is too is a lengthy affair, and cannot undo any damage done and the trauma you underwent subsequently.
Besides these three general risks there are specific surgery related risks as well – infection, allergic reactions, longer time to heal, etc.
My question is about the purpose tou need to get when you go to use the cosmetic surgery. For instance, if I use every day, I have no necessity to risk my own skin, face and others to work with the surgery. So main reasons are connected to the cosmetics view first. And then the real results.