Hiding the site domain name from the content writers I'm in dilemma. I'm hiring content writers etc for my new sites who risk getting fired from me for not meeting my expectations. I want to keep my site names confidential from the world because of competition and other concerns.

What is the best way to hide the domain name also allowing them to add the content(articles, forum posts etc) straight-forwardly at my production site ?

I was thinking to symbolic link( on my Centos hosting) another idle domain name to point to my site. I'd use relative urls in my site content so Pathauto would take of this. So the content writers would see this idle domain when working on my site.

A site can be visible from multiple domains. For example I can install the same site on my localhost PC. Secondly there are more than 50 million sites. For new sites it'd take a couple of months for a site to start appearing in the top 100 results in Google. How'd a naive person find the site in short time? Hiding the domain name means suppose I've a site name myjobs.com I want to make it visible in somejunk.com domain too and editors will add content in this site.
As long as you have your server configured properly (ie, have your ServerName and ServerAlias directives set right for Apache), then this should work our of the box as long as you don't explicitly set the cookie domain or base URL in your settings.php.  A potential complication is if you have any rewrites for canonical URLs on your site.

However, I think your best approach is to use the Domain Access module to run two sites out of the same installation.  Have one affiliate be for the live domain, and the other affiliate be for the authoring domain.  Then separate the content / themes as needed.  When content is OK, just move it from the authoring affiliate to the live affiliate.