There doesn't seem to be any default view mode at least on Mountain Lion. The view mode used for folders that don't have a view mode saved in a
.DS_Store file is changed when you open a new window or close the last Finder window. It corresponds to the
FXPreferredViewStyle key, but the key is not always updated immediately.
The always open in option should be called something like "remember view mode for this folder". If it's checked, the previously used view mode is saved in a
.DS_Store file, which overrides
FXPreferredViewStyle the next time the folder is opened.
You can make Finder forget the folder-specific view options by running
sudo find / -name .DS_Store -delete; killall Finder. It also resets the positions of windows and icons, Spotlight comments, and sorting modes.
Just don't select those always open in checkboxes again after that.