I have so many websites that got back link from facebook.com with its user name How they achieve this Backlink from facebook.
That must be a backlink which you must have saw in the yahoo explorer and not in any backlink checker site like SEO-Elite or in google. It must be a no-follow backlink. For example a link is a link from anywhere it comes from, it doesnot matter till its a do-follow link for your site. The do-follow links will eventually benefit you. Facebook and other social networks like twitter for instance, carry a no-follow tagging for their inner or profile pages. So infact, you never gain with such links, honey