I'm wondering how many people use subdomains, or do you buy a new domain name for every site/product that you promote? I'm trying to decide what way is a good idea.
A new domain.. subdomains are taken less seriously. I buy a new domain for every site idea that pops into my head. Hosting a site on a subdomain comes across as not trying to invest in your idea, don't know other people think about it though. Domains are so cheap these days, it would be a waste not to buy one..
I too agree with you that domains are so cheap now a days and its always better to register new domain is the site is specific or unique. But some times if you want put the weight on the same domain or if its a horizontal or information portal, sub-domain may help.
I use a seperate domain for each site and idea. If you just want to add another section like a forum or blog to beef up the site then a subdomain will be a good idea of course, but for a seperate project id go for a independant domain.
It depends on your aim. If you have a domain with a trustrank it is a good idea to use it for some projects (whether subdomains or the the divisions in the folders. If the your domains are new and are in the sandbox then it is ok to use other domains.