It's worth mentioning that in HTML 5.1 they are now recommending that you use headings with an appropriate rank. Not that it's wrong to have multiple H1 tags, just not recommended anymore.
Exact wording: Sections may contain headings of any rank, but authors are strongly encouraged to use headings of the appropriate rank for the section's nesting level.
http://www.w3.org/html/wg/drafts/html/master/sections.html#h...