To Subdomain or not?

Hi?
I was wondering if I could impose for some help? My site is
www.jcurranphotography.com. I have been really successful with the
sitemap program. The site went on line in July, and pretty high up in
the search pages for most of my major keywords. I don't want to change
anything I'm doing, but I recently addad a photoblog
/photoblog/index.html and it's doing very well. Rather than treating it
as a subdomain and giving it it's own verification file and sitemap,
it's included as a folder in the main site. But it's getting big, and
for organizational purposes, it would be easier to treat it as a
separate site. Will there be any negative effects from this?
As an aside, I really enjoy this group. You guys are all so smart, yet
very cool and accessible, and I've learned a lot reading the posts.
Your friend,
Miriam