Single or Multiple Domains

Ideas for which approach could be best in the long run?

[rover]

We publish information about services within a broad service area and are now expanding. The question is whether to do this on one domain with multiple directories, dozens of separate domains, or with dozens of sub-domains...Any ideas on how things might evolve over the next few years with Google, or other search engines?

I've written out for myself what I think can be some of the pros and cons to doing this with regard to getting search engine traffic from Google (and other search engine and directory sources).

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(1) Multiple Domains

e.g.
domain-service-one.com
domain-service-two.com
domain-service-three.com

Pros:

-Allows better targeting for inclusion in specific and multiple categories for DMOZ & Yahoo, and more focused theme for a domain.

-Better targeting for anchor text in links to us (for those who link to us without our suggestion of anchor text). We can name the sites on the separate domains with the keywords we are targetting, so that those who link to us will almost always have good anchor text in their links to us.

Cons:

-Hard to get decent domain names in a lot of areas. It looks a bit unprofessional to have a jumble of domains that are really long, or have dashes, or just look plain silly or spammy.

-Potential problems from Google for interlinking dozens of domains from the same server. Of course, if the content is relevant this shouldn't be a problem if Google is doing its job well, but there is that nagging concern of getting lumped in with spammy sites.

(2) Single Domain with Directories

e.g. domain.com
domain.com/service_one.htm
domain.com/service_two.htm
domain.com/service_three.htm
etc.

Pros:

-Much Simpler, less overhead, can go with one good domain name.

-No worries (real? imagined?) about potential problems with interlinking separate domains.

-Possible to get lots of inbound links to one domain getting established as an authority with Google and other search engines.

-Easier to add new areas without getting 'sandboxed' in Google when creating a separate new domain and getting it established, etc.

-Seems more straightforward and less focused on search engine optimization/manipulation.

Cons:

-DMOZ & Yahoo and other directories often will only let you list the site in one very general category, that can make relavant, practical, good sub-content almost invisible to directory users. It also seems to make the anchor text for link in from the directories less focused and effective.

-Less diversified and more risk. All eggs in one basket. If the domain gets removed, penalized somehow, then everything goes down with it.

-Does the domain perhaps lose some of its focus in Google or Yahoo because it covers many sub-areas of a main subject?

(3) Using Multiple Sub-Domains:

e.g. domain.com
service_one.domain.com
service_two.domain.com
service_three.domain.com

Pros

-I think that you can get these individual sub-domains listed in the Yahoo directory (if you pay for each one), allowing for better targeting, focus, etc. I don't know about DMOZ or other directories.

-You can go with the one good domain and create a more professional looking appearance (i.e. you wouldn't have the jumble of names that would be required for multiple separate domains). This seems to be what major companies, universities, etc. do.

Cons

-Not as diversified as separate domains? Same as having one domain with simple directories?(i.e. if there is a problem with a sub-domain, it is clearly associated with the main domain, so a problem with the domain or any of its sub-domains might also result in everything going down?)

-Are they considered spammy in nature? Do they appear to simply be a way to artificially boost search engine rankings? Any guesses on how they will be viewed by search engines in the future (next 2 - 3 years?)

-Are new sub-domains treated just like any other new domain? Same sandbox type of effect?

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I need to emphasize that our main focus and effort is in providing unique, quality, practical content that is best for our target users. Also, we don't aggressively optimize, just use common sense and approaches that don't conflict with a good user experience. Any of the three options above for structuring the site(s) has no impact on the user experience or the content we provide.

So, I'm trying to determine the better way to go in structuring the site(s), in terms of the way that Google and other search engines handle the various options now, and how people think this might evolve in terms of domain structures and their impact on performance from search engines such as Google...

[jonrichd]

I seem to remember Matt Cutts at Pubcon frowning on using multiple subdomains. If you look at some of the Hilltop stuff, you can see that it may discount interlinking between subdomains of the main domain (of course, this discounting would also take place with subdirectories instead of subdomains. (ie red.widgets.com would not be an authority link to blue.widgets.com.)

How much content will your different areas share? If a lot, might be better off with a single domain.

There are lots of other places to get links from than DMOZ and Yahoo. Plus, I believe that DMOZ will allow a site to be listed in multiple cats if the content is different, and the site's quality merits it.

Finally, remember that search engines rank pages not sites. Therefore, different pages on a site could do well for different subject areas.

Just some food for thought.

[rover]

Thanks for those insights, I really appreciate it. Initially, I was leaning toward using one domain and organizing it well (not using sub-domains), and then getting as many quality inbound links as possible and not worrying about it past that.

My one big concern,though, is having all of my eggs in that one basket. But I get the feeling that sites that have a lot of high quality, relevant inbound links are less likely to get dropped unless there is something blatantly wrong with what they are doing...