A good domain name can make all the difference, as such choosing your own domain name is very important. There are a number of good reasons for having a domain name, the following are a few:

•  You are in complete control. You can point your domain to any web host your want to use for hosting your side. So moving from one host to another become very easy.
• Having your blog or website running under your own domain name shows commitment to your work and gives credibility. For website used for business this is absolutely must as customer would be more willing to do business with such company as opposed to company having the website running out of some non-credible URL like http://www.someone.blogsopt.com
• You can created unlimited sub domains to partition specific area. In this way you can have sub domains created based on specific type of feature or content. Example you can create forums.yourwesbite.com to point your forums or blog.yourwebsite.com for your blogs and so on.
• Having own domain name, also helps bring more advertisers as they see the same determination and credability and are more willing to work.
• Own domain name helps the user to uniquely identify your website.
• Your domain name can become word of mouth and present your brand.
• A good simple domain name is easy to remember by the user and can be spread easily using the word of mouth.
• The domain name itself eventually can become a brand representation once your website is popular.
• Once your domain is registered, it is available in WHOIS database. If its under public or enhanced listing with the Domain Registrar users/business can be know about your site via database search.   

 What is a Domain Name? up Choosing a Domain Registrar