It's a very common misconfiguration, though, because it happens by default when setting up CF. If your customers are, by default, configuring things incorrectly

It's a very common misconfiguration, though, because it happens by default when setting up CF. If your customers are, by default, configuring things incorrectly, then it's reasonable to ask if the service should surface the issue more proactively in an attempt to help customers get it right. As another commenter noted, not even CF's own RSS feed seems to get the content type right. This issue could clearly use some work.