This is called "Blogger/blogspot Title Swapping". Swapping blogs title can help boost your position in search engine results page listing and also increase clickthroughs. From an SEO (Search Engine Optimization) perspective, page title is the most important element in your blog in terms of ranking well in search engines. If you look at your browser's title bar you will notice that Blogger's default templates display your blog title in front of each page or post title.