I attended a special woodturning workshop showing various methods for turning goblets. The workshop was hosted by the Chapel Hill Woodturner’s Club, and taught three different methods for creating one, two, and three piece goblets.

The different approaches are useful when:
A single piece of wood is attractive as a single monolithic turning.
Two pieces are useful when you want contrasting woods or you want a level of detail in the stem that the material of the cup can’t support, for example, an off center turned stem.
Three pieces are similar to two pieces except that, with the base being separate, you can face turn that and add details like textures that might not look good in a single stem. Also, of course, it would allow three totally different pieces of wood to be used in the piece.
Here is what I’ve produced as a result of the workshop:

A collection of goblets I turned as a result of the Goblet turning class. The two on the right are one piece goblets, while the funky one, made of Maple Burl and dyed Walnut stem and base is a three piece goblet.