i have seen many blogger have xxx.com instead of xxx.blogspot.com
how to do that any1 has any idea about this
It looks more professional and more business like and it allows you to control your SEO. Also, it enables you to integrate other services more easily.
When you start, it is ok to use a service like blogspot. Your SEO benefits from the high traffic of their domain (which is one of the multiple factors that help to increase your position) but on the other hand it is deluted for the millions of other blgos.
If you have a blog, or a site of any kind, you want to be seen and there is a point where you need to take control. The way I see it, there is a point where you need to move on.
If you look at your account there will be an advanced options area where you can configure your own domain name.
Blogspot.com is a free service so control over your blog is very limited. What people do is they buy a domain hence the xxx.com. It becomes a lot more personal and your hand is the one that controls it. Sure, you have to shell out a few bucks but it isn’t that expensive to get your own domain nowadays. 
I think they just used a template from blogspot or used Blogspot’s CMS that’s why it looks like blogspot.
I hope it’s not a porn blog 
Nowaday, you can host blogspot in your own domain. Im not quite sure on the right term to explain this, but as far as i know, blogspot will serve as a CMS for your website.
That’s what I thought also. LOL.
I didn’t know that you could do that with blogspot… That service wasn’t available when I had an account there… Interesting
Yet, the answer is the same. If you have your own domain looks more professional, and it is more direct to your target public, so it is just a natural choice, in my opinion.
If you move your existing blogspot blog to your own domain do you lose the PR… I have a PR4 blogspot and was thinking of moving it to my own domain but feared that I might lose the PR and traffic… 
Yes, you will lose some of your existing PR when you migrate your blogspot domain to your new URL. However, it will come back eventually. There is a feature in the settings section where you can point your blogspot blog to your new URL. Both stay active, but the blogspot just redirects to your new domain.
Blogger itself guides you to do this. In settings of your blogspot account, you will see option to buy a custom domain. follow the guidelines given there that would be better.
well i may not agree to this because i have personal experience of moving around 5 blogs from blogspot to custom domains. i did not lose PR for even one.