At pubcon, Matt Cutts of Google just announced that they will start limiting search results to two subdomains for any one web search. This is a drastic revision, and may very well affect your site, possibly very negatively. Thankfully, the announcement specifically stated that the changes would be rolled out only in the next couple of weeks, so you still have time to prepare.
What This Means
In the past, search engine results have treated subdomains as though they were different sites. If your company is QWERTY, Inc., for example, and you sell widgets and fizzsnaps, then you might use widgets.qwerty.com as your widgets site, and fizzsnaps.qwerty.com as your fizzsnaps site. In this way, you could keep using the same branding for all your sites by using the same domain, but use different sites for each product.
But now, that logic has been perverted by google’s recent announcement, because now, no matter what the search is, your domain can at most occupy two slots on any search engine result. Which means a search on “qwerty”, for example, would at most show the www subdomain and your most popular other subdomain. Other slots will go to other people’s sites.
Even worse is if you do not own your own domain, but are just renting out a subdomain–now, for any given search, you are almost GUARANTEED not to get into the search results AT ALL.
How To Make Sure Your Site Does Not Take a Hit
If you are currently relying on subdomains for the different departments of your site, now is a good time to start thinking about setting up different domains for each of your departments. Do not abandon your old sites, especially if you have long term seo investment already in them, but start up new sites with unique one-page content on each, that links strongly back to your old domains. Once these pages reach sufficient pagerank, they should be able to replace the positions that you will have lost from Google’s drastic change.
If, however, you unfortunately are hosting your site under a mere subdomain, then this is the call for you to get your own domain. When this new policy rolls into place (Matt Cutts said it would be “in the next couple of weeks”), your site will be effectively dropped from all search engine results, period. The only way to fix this, unfortunately, is to get your own domain.