DDoS is Distributed Denial of Service attacks.
It's when a botnet (a network of virus infected computers) spams another network or IP address with the intention of blocking access of genuine users. A DDoS attack can take down a lesser network.
When ARR launched without the necessary infrastructure in place, the servers/network collapsed just like as if they had been DDoSed. Square Enix blamed poor performance of FFXI on a DDoS attack in the past, and I believe WoW has claimed that it had several DDoS attempts over the years as well.
Chuckling at the Obamacare issues here because they're basically getting DDoS'd, too. If SE's servers blow up with a few hundred k players, imagine what DC's servers are doing with 18 million+. Though the general message seems to be, "IT'S A FAILURE, ABORT IT!" when it actually seems more indicative of the interest.
It actually is a failure, its neither affordable, nor care.
While I won't go too deep into it, my main point was that people do want reform, hence the site spam and subsequent DDoS-type errors you see the news talking about, but never quite explaining them that way. And while the mechanics of the ACA vary as Cat said, my biggest gripe with it is the fine imposed on people who don't get insurance. I need to follow up to see if there's an exemption for people in unemployment, but really...
As someone who's worked in the logistics end of the medical field, the system is totally ****** up and we absolutely need reform. Call me a socialist commie ******* for thinking that, but when a severe illness or injury basically ruins your life financially, it's sad to think dying might be the less cruel option for these people and their friends/families.