Build entire website in Marketo?

No, this is not an intended use of Marketo. Marketo offers Web Personalization that you can do on other webpages, Munchkin code for tracking, and can sync to Google Analytics. I don't see why you would think it would get much better on Marketo vs non-Marketo when they are built to work in that way unless your system isn't setup right and you are having issues with any of those functionalities and then we could try and help get those issues sorted out for you.

I guess it depends on the size of the site.  Anything greater than a handful of pages would be a nightmare to maintain.  Marketo really has no CMS capabilities - and was never designed to do so.  Marketo is fully integrated with our website CMS, Sitecore.  And in fact, provides better analytics than standalone Marketo reporting (when you also include Google Analytics, and in our case DemandBase).  For anonymous visitors, you're still going to be very limited as to what you can report on in Marketo.  Also, Munchkin is contained on every page of our site (~30,000 pages) and all forms are Marketo embedded forms.  The only limitation is form pre-fill (which we disable anyway to adhere to the strict privacy laws that are in place throughout the world).  Because we use Sitecore, personalization capabilities are built-in (for both known and anonymous visitors).

Has anyone built or heard of building an entire website using Marketo and no CMS? Not just landing pages or a microsite either. The reason being better analytics, progressive profiling, and personalization on all pages.

Chase, I'm def'ly going to come to the same conclusion as Chris and Dan, but for different reasons.

I don't think that Marketo not being a web CMS is reason alone to not host complex sites. Static site generators such as Jekyll and Hugo are powering very complex sites whose "dynamism" comes from both build-side and client-side (JS) templating engines.

(We use JS templating on top of Marketo templates to create dynamic personalized context, including lead tokens, segments, remote data feeds, etc., although those are admittedly still dynamic LPs.)

When you author and compile your site using these tools, the result is a set of highly scalable (since there's no server-side action necessary) and yet still totally dynamic (since the content on the page can be assembled in the browser from dynamic sources). If you combined this static output with Marketo's ability to embed {{lead.tokens}} and {{my.tokens}} into the output and change content blocks based on segments, you could create an amazing site. I guarantee it would be mind-blowing.

BUT. There's a problem. Site generators expect some sort of traditional upload/publish interface, be it network file share, S/FTP, SSH, or Git push. Marketo's Asset API is so proprietary that you can't integrate it into the traditional dev-staging-production process.

With a comically complex amount of effort, you could presumably build a proxy between SFTP and the API, but... don't. Instead, you should step back, choose another publishing platform and/or CMS.

Not to say the things a CMS can do aren't also important (particularly when dealing with internationalization). But to me, "complex multi-page site" doesn't have to mean "CMS-driven site", so the top deal-killer is the lack of interaction with development tools. It's a shame, because there are a lot of quite deep brochureware sites that would benefit from segment- and lead-awareness, and direct knowledge of where a lead is in the cycle, and they don't need a CMS per se. They just need something that's maintainable.