A big reason for the subdomain is that these days it's all about getting found when someone is searching for something that you sell. There is a lot of "fu" th

A big reason for the subdomain is that these days it's all about getting found when someone is searching for something that you sell. There is a lot of "fu" that goes into how Google decides what results to return for a given search, and how Google decides what page or site is the most authoritative for a given search. While nobody knows the exact recipe, everyone seems to agree that your domain name plays into the algorithm significantly. When you spread your content across domains, you're essentially diluting the search value you can achieve for a given query. Maybe it doesn't matter today, because you rank very high now, but that may not always be true. The other reason is that people will bookmark your blog (if you're lucky ;) ). What if you later decide to switch from wordpress.com to whoknowswhat.com? What if wordpress goes out of business or shuts down for some reason? People will have bookmarks for what is essentially YOUR site on a domain that you ultimately have no control over. It is a bad idea to build up a resource for your company onto a mechanism that you ultimately have no control over.