Forum - is Subdomain or Directory Better for Google SERPs?

[apauto]

Ok guys,

I have been doing a lot of research, and I can't figure out what would be the best for the long run.

Here are two threads I have used for reference:

[webmasterworld.com...]
[webmasterworld.com...]

Here is the scenario. I have a website that sells different types of widgets. This site also has a web forum. The web forum is growing pretty quickly through some clever marketing, and I am very happy. However, I do have some concerns, and want to nip it before the forum gets any bigger.

If I have the forum in the format of example.com/forum and this subdirectory has 1,000,000 pages vs 10,000 pages of the ecommerce site. Will the ecommerce section suffer in rankings since it gets diluted by all the forum posts and topics?

Should I move the forum to it's own subdomain such as forum.example.com and have a 301 on the current subdomain?

Which will be better for SERP? I'm just afraid the site is going to rank lower and lower for the important pages (ecommerce), and rank higher and higher for the forum pages (not as important), and a subdomain might do the trick. I'm worried about the subdomain, because I have read that this can hurt some page rank, as people will be linking into the subdomain and not into the main domain.

I would appreciate some of your advice, so I can decide what to do once and for all, and move forward.

Which would you do for the long run? Which would get me the best exposure, and at the same time the best SERP. I'm sure some of you have been in similar situations.

Thanks in advance WW!

[edited by: tedster at 8:11 pm (utc) on Oct. 7, 2007]
[edit reason] switch to example.com - it can never be owned [/edit]

[tedster]

I just did an inurl: search so I could see what the most widespread practice is for top ranked forms - and it is using a subdomain, by a wide margin. One advantage with a subdomain is that if, for some reason, the subdomain catches a penalty, it doesn't necessarily affect the root domain. With a subdirectory, it is much more likely for trouble to affect the entire domain.

That said, a domain's internal linking is a big part of how Google decides what pages are the most important. So if you stay with the current directory set-up, I would give some thought about how you offer links from the ecommerce directory to the forum.

For example, you could offer links to the forum with an iframe so that even though your visitors get a link from every page, there's still only one link. Then you could offer links from forum pages back to your ecommerce pages in the normal way. I think that linking structure would send a message about the relative importance.

[apauto]

I value tedster's comments, but would like more discussion... anyone?

[supafresh]

Aren’t sub domains looked at by google as independent entities?

If this is true then any link building done for your main site would not apply to your forums. A link from your main page would pass some PR from the forums but you would have to start over with link building and go from there.