Hi,
To put it simply, anyone that is looking to benefit from SEO will not be using a one page website.
After the keyword research has been executed, how would you outrank the competition for 50+ diverse search terms all stemming from one page?
In the world of SEO, it is general knowledge that you can only realistically optimise a single page for only a handful of search terms.
And in my opinion, even the user experience is debatable as the user is forced to re-evaluate the way a site functions (clicking a link triggers a scrolling effect for instance).
For me personally, one page sites are a major no no, unless of course you're not looking to SEO the site.
Regards,
Anthony Ankers