Forum Moderators: open
Yes, putting all your page content in divs and changing their visibility onClick would make a quick application - but it also puts everything in one big HTML document which is a disadvantage with search engines.
For one thing, even if someone does get your BIG page in their search results, when they click-through they may not see their search term -- and then you've lost them.
For another, having links between separate pages is the standard web metaphor and you get to describe the content of various pages with your link text, title attributes, etc. Each page is a separate chance to get a new visitor from the search engines.
While you might want to use this scheme in one small section of your site for ease of use (assuming you're not adding too much file size), I'd advise against it as a site-wide strategy.