The Alice case seems to have set the precedent for invalidating a number of software/internet patents. I am curious what this implies for ideas (as well as implementations) which are obviously unique, specifically, in the case of such things as such as HotOrNot, user-rating/ranking systems, etc.
As a general guide, judgments that start with "The Court has long held ..." don't add much new to the law.
You have never been able to patent an abstract idea, you need an invention. That is, a specific implementation of an idea: it doesn't have to be realised but it has to be realisable without further need for invention. This means that, armed only with the patent and normal professional/technical knowledge someone could actually build it. Similarly it must display ingenuity, you cannot patent things that are obvious.
Despite the best efforts of patent offices many patents are granted that may not meet these criteria: that's why a patent can be challenged in court. An invalid patent may stand for many years (or even expire) without ever being reviewed by a court.