What's more interesting is that blogger staff has never bothered about such a big issue in past, and lot of popular blogs might have lost millions of visitors due to this small bug. Good news is that finally blogger has added a feature using which we can redirect http://domainame.com to http://www.domainname.com or vice-verca.
all you need to do is to go to your settings tab, click on Publishing and check the opion Redirect domainame.com to www.domainname.com.
It takes few hours to get fully functional, but it does work fine. If you are using custom domain name bought using google checkout at godaddy.com, then you don't need to worry as it works fine by default.