Are massage chairs bad for you?

No. They are not bad for you. Getting a massage on a massage chair is a bit different than lying on a table. For example, the massage will be shorter and will focus more on rejuvenating and energizing you so you can feel refreshed rather than sedated, which is more likely going to happen in a longer massage.

If you are a practitioner, then they are not bad for you as long as you know how to use them and set your massage program. Also, which brand are you buying. I own a massage chair from OSIM which I use regularly and it hasn't caused any problems for me. OSIM Massage Chairs are really worth the spend.