There are some soft tissue injury accident cases where you may be able to represent yourself. If you have a minor soft tissue injury such as whiplash that consists of a sore neck for a few days and little more, this is the type of case that you may be able to handle on your own with the insurance adjuster.
That said, there are many other times where a more serious whiplash injury should involve an attorney on your side, and his expertise will probably net you more money even after he takes his contingency fee. Insurance companies notoriously dislike serious whiplash claims; they involve a lot of doctor visits, chiropractor visits and physical therapy, and the injury does not show on x-rays. So, if your whiplash is causing you weeks or months of pain, you really should hire an attorney.