As a 40 year resident I can say things have changed in ST Thomas over that time for sure -- but not to the level of recommending a tourist should bring Mace with them or really anticipating any kind of criminal confrontation while on vacation.
The criminals here and everywhere in the Caribbean are much better armed than they were 10, 20 or more years ago, without a doubt - but almost all of the crime seems to be gang, drug or vendetta oriented with very few crimes against tourists occuring - a good heads up street awareness and common sense in where and when you are out and about is a simple precaution - late, late night bar hopping and overindulging is not something I can say is safe anymore - and I speak from the experience of bartending the 10pm - 4am shift for many years in the 70's and 80's here - I wouldn't go out like that now.