A portal does differ a little.
A portal can create a feeling of belonging
A portal can enlist users to assist with
SEO in subtle ways. I think a little more thought in creating user loyalty.
If a portal contains user web pages for instance, I expect that making sure that they had the tools to place links, etc would be a useful
SEO tool, encouraging users to list the section of the portal on their email address . or even supplying an email address for them. (this is a regular feature on many great Portals)
I think there are a few things that a portal could consider, that are as pointed out normal procedure. but I think a little more emphasis on creating a feeling of loyalty could be well worth the
SEO effort.
For example if you simply sold Tennis shoes on your web site, getting your users to place
'bobby@tennishoos.com' would be extremely difficult. But
bobby@yahooo.com is a different prospect.
I see a growing number of posts in forums where the poster has listed his portal page - giving users instructions on how to do this, and why to do this. would be an asset.
I fully agree with the earlier replies. but if there is a difference. this is where I suspect it would be.
(empasis on user help)