When is a blog not a blog?

Q. When is a blog not a blog?
A. When it is a blog post

There is not much that brings out the pedant in me but when people refer to a blog post as a blog it drives me nuts! I get caught out all the time when someone says "Have you seen my new blog?" and I think they have set up a whole new blog when in fact all they have done is write a blog post! A blog is the whole blog with all its posts and a blog post is a post - OK!