Do I have to use H1 for post title?

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Michael Martinez: If you`re judging by the original Hx specification, H1 is intended for the most important headline on the page (as in a classic essay outline). It was never intended to distinguish one page`s main heading from another page`s main heading. As far as the H1 specification is concerned, you can publish 1 million pages all using the same H1 text. The search engines will scan the page and digest it according to their preferences. They may or may not take the implied structure of the Hx hierarchy into consideration. They may or may not infer emphasis from the use of Hx heading markup. They may or may not treat each page as if it`s about "dog care blog" or something else. What you put into the H1 or H2s doesn`t carve rules of interpretation in stone. I would not argue with the client over their preferred markup. This is not something likely to cause a lot of SEO headaches. If, however, they are frustrated with their site`s performance and are feeling anxious, then the old adage of "if whatever you`re doing doesn`t work, try something else" can be very persuasive in a non-confrontational way.
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  Linda Caplinger: But the page value of those 1MM pages with the same H1 tag is low. You wouldn`t have a book where you name each chapter the same thing.
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  Michael Martinez: Linda Caplinger There is nothing about a similar or duplicate H1 element that renders a page`s quality or value as "low". "Low quality" means something very different to a search engine than it does to the average Web marketer.
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  Linda Caplinger: If a page is constructed correctly, the H1 tag is the theme or topic of the page. If all of the page have the same H1, and same theme or topic, I would say it has lower value. If you have the same H1 tag but different content, then the H1 tag is rendered useless as it`s not accurately describing the content.
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  Michael Martinez: H1 elements are optional and search engines index billions of pages that do not have them. There are no hard and fast rules for page design.
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  Nimie Gill: Ok, good info thank you, Michael Martinez