Selected answers from the Dumb SEO Questions G+ community.
Micah Fisher-Kirshner: On each crawl to your home page, Google will know the textual changes made, so there`s no real need to address that.
Alan Bleiweiss: Changing the publication date is an artificial form of manipulation. There is only one publication date. There is a "last modified" tag, however Google ignores it.
Jeremy L. Knauff: Google can tell when it was last updated because they have the last version cached. And they likely store every version they`ve ever cached. So you`re making unnecessary work for yourself that has no benefit.
Loren Baker: Do Not change pub date if there is no content update. Have seen sites drop dramatically for that as it`s a recognized form of manipulation. Only change when content (maybe 20%) has been updated and ALWAYS include an "this post was updated on <date>" sentence.