@sazius: priceline.com, hotwire.com, and the like integrate several thousand airlines, hotels, car rental services, all kinds of things, with prices and availability that change constantly, 24/7. I'd say that's at least on par in terms of complexity.

healthcare.gov has had three and a half years to get it together. This is an embarrassment. It's inexcusable. But as @lnxwalt said, it should shock no one.