Agree, in my experience storage buckets are always private by default, and you must take several specific steps to make them public, ignoring the very big warnings sprinkled in each confirmation page along the way.
Are there any cloud vendors that don't follow this approach?
Almost all of them.
A good example is Dropbox link you send to someone. I could generate this link to a private file in my Dropbox, email it you, and Bing (may) index it.
Are there any cloud vendors that don't follow this approach?