shouldn't be, although I wouldn't go and started abusing them. I find it's normally best to stick with a single pair of H1 tags, as it signals the title of the page to the SEs
only use 1. an h1 tag should reflect the page title. h2 or h3 tags should reflect the topics on the page.
This is a guide and not suppsoe to be taken literally but throught a recent study (or atleast when the article was written) Here is what this article says about weight of tags. http://www.nerdlib.com/seo_tips.php
<h1>Main Heading</h1> Main Heading <p>First paragraph content.</p> First Paragraph content. <h2>Sub Heading</h2> Sub Heading <p>Second paragraph content.</p> Second paragraph content. etc...
Although there is no "rule" against it, multiple use of the <h1> tag dilutes the power of it. Keep the single <h1> tag that matches the page's <title> and go to the <h2> tags to do this. This will always work for you.
The <h1> to <h6> tags define headers. <h1> defines the largest header. <h6> defines the smallest header. normally best to stick with a single pair of H1 tags use.