Here/there is OK. Sugarless gum is probably not a bad thing..But anything in excess is not a good thing. Sugarless gum contains sorbitol...A laxitive and so excessive use may cause some stomach/intestinal upset etc... Also, excessive chewing will strain your jaws/tmj, wear-out your teeth etc...So, moderation, rorome! be sensible, stay healthy... Good luck.
CAN BE A CONCERN. Chewing gum, especially sugarless, normally cannot really be bad for your health, but... If you put too many wads in the mouth and chew at the same time or chew only on one side of the mouth, other problems can ensue. Tmj/tmd symptoms may develop and the health can suffer in a domino type effect.