I currently run a webstore on shop.sproutsoup.com. I have a blog and informational pages set up on www.sproutsoup.com. The shop site does relatively well in the search engines. My next big task is link building, I'm sorely lacking. As I'm thinking about building links I realize that most good, natural links would be to the informational pages on my main domain, not to the shop subdomain. So first question: Is having these two domains a bad idea? My intent is obviously to increase sales in the webstore. Would I be better off in the long run to combine them and have informational pages and commerce pages on the same domain so that incoming links for the informational pages help the commerce pages as well? Or is having links to the products I sell on the subdomain at the bottom of these informational pages good enough? Second question: As I'm building the informational site, I had considered creating a few more subdomains so that some of my "bigger" keywords could be used in the domain name. For example, a keyword like "Baby Carriers" gets 100+ searches a day and currently I don't rank for a term this broad. Would creating baby-carriers.sproutsoup.com with informational pages about the subject help? Or would www.sproutsoup.com/baby-carriers/ be better so that I'm not spreading my links across multiple domains? Are there benefits to having a subdomain dedicated to a particular subject so that domain begins to rank higher for that subject? Or would the amount of links I would need to have going between a handful of subdomains negate any benefit? Thanks!
A subdomain is treated as a completely new domain as far as the engines are concerned. That being said, you'd be subject to the theoretical sandbox, etc. The good side of all of this though, is that if you can get your PR up on both subdomains you have double the leverage for future domains/subdomains. Personally, I've had much better experience keeping everything on the same domain (I don't even use www.) but your mileage may vary. I've heard of others that do better splitting things up.
Golfboards is right that SE see a sub-domain as a separate site. It really becomes a trade off. There are advantages to having a bigger site with more pages. And there are advantages to having links from related sites with differing domains (which a sub-domain would give you.) FWIW, my limited personal experience hasn't show much difference. We moved several sections of our site to subdomains and they have the same PR as the sections of the site that are in subdirectories.
I wouldn't combine them. They're already doing pretty well and you wouldn't want to do 301's to all new pages under the main domain. That being said, I'd start getting links to your product pages and subdomain homepage. I don't really think it's necessary to create another sub-domain. But, it kinda depends on the structure of your site. If you're a portal, I can see where sub-domains fit. But if you're just talking about baby products, even if its all sorts of baby products, I'd say just create folders of the main domain and continue building out. Get links to those folder pages using your proper anchor text and you'll be fine.