At least on Mountain Lion, there doesn't seem to be any default view mode. The view mode used for folders without a view mode saved in a
.DS_Store file is changed when you create 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 to a
.DS_Store file, which overrides
FXPreferredViewStyle the next time the folder is opened. It only applies to one folder, or doesn't affect any folders under it.
You can delete the folder-specific view options by running
sudo find / -name .DS_Store -delete and quitting and reopening Finder.