In this talk on the cybersecurity of healthcare.gov, they mention that the website has been attacked a couple of times. The examiner is reporting that many of the those attacks are by right wing groups.

This is a (Distributed Denial of Service) DDOS attack:

DDOS attacks on healthcare.govS

It's when people send a whole bunch of fake traffic to a website, thereby flooding its servers so that it can't handle legit traffic anymore. Many of the complaints about healthcare.gov are about the designers underestimating the amount of traffic the website would get. So, putting 2 and 2 together...some of the trouble people may be having logging into the site might not be 'cause of the admittedly bad architecture.

Image source: ddos-protection.org