Subdomain vs Subdir, rehashed

Directive from boss. Need pros/cons.

[webg]

(I searched for info but didn't find exactly what I was looking for, so I'll reopen this can of worms. Apologies in advance to those who've been through this before.)

Boss has told me that for advertising/marketing purposes that we would like to start using *both* custom subdirs and subdomains and have those both redirect to specific content pages on the main www site. The subdirs and related subdomains would not be used internally or on the www site itself, but might be linked to from external sites.

Bad Example:
- Destination page is www.storename.com/health/toothpaste/crest.htm

- both crest.storename.com and www.storename.com/crest would redirect to the content page.

- oh yeah, there's also a keyword 'crest' that works directly from the internal search engine, available from all pages ("visit www.storename.com keyword CREST for information")

So, in the big picture, we're not changing the site around or breaking it out into subdomains and all that - we'd just be doing a ton of redirects. What problems or concerns or benefits should I have or expect? (losing referrer information? SEO penalties?)

If it helps, I'm against this suggestion. But since I was told to do it, I need to come up with better reasons why it's a bad idea other than "It's stupid."

[MatthewHSE]

He wants to use both? Sounds like a bad idea to me, just for usability and consistency. If both are used for marketting, etc., it could easily cause confusion. Try to get him to go with one or the other, but not both. (I prefer separate sub-directories myself. We had a good thread here awhile back about sub-domains, which of course I can't find now, but basically the consensus was that they result in a lot of confusion among some users.)

About the redirects, just set them up in your .htaccess file as 301's. That should eliminate any potential duplicate content issues or similar SEO concerns. It is likely to get messy if you have very many redirects to mess with though.

[webg]

You funny, but only because I didn't clarify one important piece: runnning on IIS, so can't use the fun .htaccess file either. Which means lots of internal IIS configurationing.

Hmmmm... this looks interesting.
www.isapirewrite.com

Although I could probably do the same thing with a custom 404-error page. (if /foo then redirect to /bar/foo.htm)

But I digress, as the issue isn't *how* to do this, but rather "why or why not"?