In any event I will not going to examine Digg's particular patent because I do not want to get PG in trouble. But, as I said patents tend to be much narrower than non-specialists assume, so if someone mentions a patent, you should not panic but get a competent patent lawyer to determine what the exact scope of the patent is. Usually, it is not as bad as it seems and often you can get around it.
Of course, I am speaking in generalities and individual cases may vary, but when people come to me with patent problems I often find a way to avoid a patent.
When non-specialists talk about patents they usually interpret the patent coverage based on the title or the summary, but the actual scope of protection is defined by the claims and it is usually much more narrow than the title suggests.
I expect you'll say what lawyers always say, which is "it depends", but it's my question and I'm sticking with it :)
Ps i have to say that this is not legal advice and if you are asking this in relation to a real case, i strongly suggest you contact an attorney.
1. Does the infringing party have a stash of money to pay for a quick settlement but not too much money that they could send a battalion of lawyers to countersue?
2. Is the infringing party a strategic competitor?
3. Is the infirning party holding a stash of patents of their own that they can sue you with?
4. Is suing the infrigner worth the risk of losing the suit and therby possibly invalidating the patent and therby making it worthless? You got to know when to save your ammunition for the real fight.
By these criteria HN and Reddit probably do infringe but is not a concern of whoever is holding the patent.
Fact of the matter is you can sue anyone for anything if you can afford the lawyers to do so.
The first claim, which all other claims depend on, only claims the invention when 1) The voting patterns are being displayed in a "swarm interface" 2) The "thickness of a line" is used for visualizing the number of votes
I don't believe that any of the modern sites use a swarm interface at all, and if someone wanted to show a swarm interface, by using something other than the thickness of a line for the visualization, you've sidestepped the patent.
It's hard to believe someone paid good money for this.
True, and the article mentions 15 patents, so the remaining is hidden somewhere in the USPTO database.