The containers Vitamix uses are made from fiberglass. Fiberglass is used for many purposes and therefore comes in different forms. Fiberglass that is made for food
is recommended by food safety experts for use by campers and for those storing water long-term, such as for disasters.
The dangers of fiberglass appear to be related to the ability of loose glass (dust, fibers, particles) to enter the lungs. This hazard exists during the manufacturing process and also wherever loose particles can exist, such as in buildings where fiberglass insulation is used.
I remember when I was a child that fiberglass was a big issue, but from what I have seen/heard/read since then, the danger is not with the molded fiberglass containers used for foods. Maybe you can find information about fiberglass food storage containers that says otherwise, but I haven't seen anything thus far.