It's not addicting in the same way cigarettes or cocaine are. However it can be addictive behaviorally. When you take LSD, it mimics your bodies natural serotonin, however acts differently than regular serotonin. In the brain, it causes different action potentials to be possible, causing thoughts to go on very different paths that your mind isn't prepared for or used to. Whether you'll become 'addicted' to it or not depends entirely on your experience under the drug. The brain is constantly trying to come to mental equilibrium - a balance of the electrical impulses that become thoughts - and LSD can mess that balance up quite a bit. That loss of balance forces the brain to try and correct itself.
Correcting itself all depends on what your mind mathematically feels is necessary. For most people, that'll mean cutting back on LSD, replenishing serotonin through sleep and diet, and taking it easy. For a few, who had a different electrical charge, it will mean more acid. Those who feel the need for more and more are often caught up in the thought processes that LSD causes, and the only way to make those thoughts 'complete' or 'whole' is to balance them with more LSD (or so your mind might tell you).
With that said, some people survive quite well under the constant influence of LSD, while others get lost in a hellish experience that may take months or years to get out of. When I first started taking hallucinogens, I ended up taking LSD almost every day for a month straight. While that sounds like hell to a lot of people, dangerous to others, it was absolute bliss to me while I was under the influence. I felt like a prophet, an all knowing master of the world around me. Coming off it is when things got weird. Training my mind to run on the constant influence of a false serotonin made my thoughts mush when trying to get back to a normal chemical balance that my brain had been un-exercised to.
And that's where the behavioral addiction comes in. You're not going to have withdrawal symptoms from it, so much as reality will not come in as clearly as you're used to without it (with excessive use of course). It's all based on your experience with the drug.
If you plan on taking it, I would recommend never taking more than two or three hits. More than that, while it might seem like your mind can handle it, is excessive and exhausting. I would also recommend not taking it several days in a row, ever. Your mind needs to replenish after any trip. Constant use of any synthetic biochemical confuses your body unless it becomes part of it's whole chemical balance. When it comes to something like LSD, you don't necessarily want to make it a part of your daily chemical balance since your body can't produce it on it's own. It's self defeating.
Take it, enjoy the experience, and wait a while before taking it again.