Why are most thumbs in ZenPhoto square?
Random images, new images, etc.
Album thumbs, image thumbs (in most themes)
Aside from some old 6x6, or similar, square film cameras, I cannot think of any square "sources" (film or digital). I do not manually crop my images to be square. I shoot with a standard rectangle shaped sensor and used to shoot with standard rectangle shaped film.
I compose my photo to take advantage of the entire image, normally the subject is off center along the rule of thirds. When cropped into a square thumbnail any focal point that is off center and to the left or right is then not balanced or is cropped into pieces with only part of it visible.
ZenPhoto seems like it is made for photographers, yet the photos that we want to share in it are altered apparently for aesthetics.
Are aesthetics more important than the photos we are trying to display?