Header tags are a great way to help boost your search engine rankings. If you're creating a page about "free hats" and would like to rank for it, there's nothing shady at all about including a nice big <h1>Free Hats</h1> at the top of the page to make sure your users and the search engines know what your page's subject is. However, as with other search engine strategies, it is important not to stuff too many keywords into these tags. A good rule of thumb is to include no more than 3 or 4 <h1> tags per page, and always have at least a paragraph or two of text between your header tags.
A page that consists entirely of header tags looks pretty spammy to search engines, and it isn't very useful to your visitors.

source ;- http://www.tizag.com