Like any electrical appliance, particularly stoves, ovens and anything with heating elements you must use care in where you locate it.
You can use the smoker on a wooden deck however there are inherent risks and dangers. What if it gets blown over by a gust of wind? What if someone trips on the cord and jars it enough to cause the butt to slide within and drip fat on wall or element? I don't mean to sound paranoid however it is essentially a portable oven and can start fires for a multitude of reasons.
My practise is to always keep the smoker elevated off structure such as decks by placing it on a steel table/tray. I never place it close to my home or anything else I don't want to see burnt up. For example I wouldn't place it on my sundeck against the house wall and under the eaves.
Although these smokers are said to be such that you can set them and walk away for hours on end I never do that. I plan my smoking so I can be busy doing other things around home and keep a close eye on the smoker at the same time.
Yes, put it on your deck. Just get it up off the floor, make sure it's secure and people are aware it's there and it's on. Check it regularly for safe and correct operation and enjoy.