Habraddiction — a severe form of mental disorder, starting with the registration on Habr.
Uncontrollable desire to visit Habr;
The mood swings directly proportional to the karma change;
Daily visit to the rating page;
Appearance of euphoria when your post is on the main page;
Looking for up and down arrows on LJ comments;
A strong feeling that you are being watched by the UFO.
(The list is not complete and can be expanded)
Treatment: at the moment effective methods of treatment are unknown.
Habraeffect — a sharp increase of the site traffic after the link to it appeared on Habr.
The bad side of this effect is that due to a sharp increase in traffic to the site, huge traffic is generated, turning into an unintentional, but non-harmless DoS attack.
The Habraeffect is most often observed for several dozens of minutes, but it can take up to several hours. The influx of users may not pass and during the day or two, until the news with the resource's address disappears from the main page of Habr.
There is an opinion that only new and untwisted websites with low capacities are affected by the effect, but this is not so. At one time, the habraeffect was able to take down a lot of large projects. About all the cases you can learn from a simple search query on Habr.