If you published your blog to the root of the domain ("xxxxxxx.com"), you'd have no content for the "www" alias ("www.xxxxxxx.com") - and if you published to the "www" alias, the root would, similarly, lack content. It was a significant day for many custom domain bloggers, when this discrepancy was eliminated.
This deficiency was most noticeable because BlogSpot blogs have traditionally provided content to both the "xxxxxxx.blogspot.com" and "www.xxxxxxx.blogspot.com" aliases, for any blog with name "xxxxxxx".
When custom domains were further enhanced, so you could publish your blog to somewhere other than the root or "www" alias, aka "Additional Virtual Host", the need for publishing to "blog.xxxxxxx.com" and having "www.blog.xxxxxxx.com" redirected to "blog.xxxxxxx.com" - or conversely publishing to "www.blog.xxxxxxx.com" and having "blog.xxxxxxx.com" redirected to "www.blog.xxxxxxx.com" - was a built in requirement.
Recent reports from Blogger Help Forum: Something Is Broken makes this earlier accepted convention appear to not, consistently, be true.
Some bloggers are reporting that, having published to "blog.xxxxxxx.com", they were then offered the option to
Redirect "xxxxxxx.com" to "blog.xxxxxxx.com"?I experienced this once, tried it, and found that, yes, "nitecruzr.net" did redirect to "test.nitecruzr.net". Needless to say, I didn't leave it published that way, for long.
Some bloggers have reported that, when given the option to
Redirect "xxxxxxx.com" to "blog.xxxxxxx.com"?they were alternately able to publish to "www.blog.xxxxxxx.com", then were given
Redirect "blog.xxxxxxx.com" to "www.blog.xxxxxxx.com"?This is a non symmetrical option, but it will work. The blog will contain internal links to "www.blog.xxxxxxx.com", but "blog.xxxxxxx.com" will redirect as suggested.
If your virtual host published blog gives you these options, try them. You can still advertise the blog as "blog.xxxxxxx.com". It's odd, but better that than having the root "xxxxxxx.com" redirected.
With the blog published to "www.blog.xxxxxxx.com", but your readers given "blog.xxxxxxx.com" for a URL, you may have a problem with search engine reputation. So having followed the above workaround, use Google Webmaster Tools, and the "Preferred domain" option to correct the search engines back to indexing the blog as "blog.xxxxxxx.com".