Just had a quick look what spine / neck cracking does. A FAQ has an interesting entry labeled Avoid Self Adjustmens:
Q: My son is constantly cracking his own neck. Besides being annoying, is this damaging his spine?
A: Repetitive and excessive forceful cracking of any joint of the spine can lead to a stress injury overtime. Unnatural movement of the facet joints (the spinal articulations) can create inflammation in that area.
The need to constantly "crack" your own neck is usually due to the fact it feels uncomfortable. The irritation reappears because doing it to yourself doesnt correct the condition of spinal tension. Our office treats neck conditions, more commonly found in teenage patients that have the habit of repetitive cracking. Over stretching the joints irritates surrounding soft, tissue (ligament and muscles) and may make the joint hyper-mobile. The increased movement can prevent stability in the vertebral joint causing it to misalign and eventually subluxate (create neurological irritation). When the vertebral subluxation complex is created, chiropractic adjustments are the most appropriate treatment.
Obviously cracking your spine yourself doesn't correct the condition of spinal tension because us crackeres feel the pressure again after only a short moment has passed. Cracking is really only temporary relief. Can a professional chiropractic correct this as claimed for good? I have my doubts.
I don't believe that if chiropractors looked deep down at what they were doing, they would see what benefits or things they were helping with.
With the back thing, if you try and get those hard cracks consistently then you are probably doing damage.
I'm a young teen and i crack my neck but i would never go to a chiropractor unless they have 100% proof it would help me. I might, when i see my doctor next in a few weeks, ask him/her about it.