I have a webpage that I use h1 tags multiple times within various DIVs and I style h1 for each div to be the appropriate size.
For example...
#conten
Semantically, I prefer using one h1 on the page, mainly for the title of the page. It probably doesn't matter too much with SEO, and with the way html is going with HTML5, the generic header tag will make it much simpler and this argument obsolete.
header