The concept has to be novel to be patentable. You cannot get a patent on something that is already publicly known.
Existence of information on a publicly accessible website (even if not indexed by a search engine or behind a pay wall like for a journal publication) is considered to be public knowledge and a patent cannot theoretically be obtained on the concepts covered by that website.
Yes. However, what's novel is subjective. The patent clerk may not care and has only a few hours to look up prior art. Once you've got the patent you get a jury in Eastern Texas to decide; that's where many of the cases end up. Something that's obvious to us will often be novel to them.
Those are indeed the practical issues the system is facing.
>> Something that's obvious to us will often be novel to them.
It should be noted though that the requirements for patentability include the invention being non-obvious to those "skilled in the prior art". The jury deciding upon a case may not be skilled in the prior art themselves, but they need to judge if those actually skilled in the prior art would have found it obvious at the time of the patent's priority date. But again, that's just theory facing the practical issues you noted.
Hmm... that makes me wonder what would happen if the system required the jurors to be skilled in the relevant art. I suspect that even if they limited that to people listed as inventors on at least one patent in the relevant area, that the result would be dramatically anti-software patent compared to the status quo.
> AFAIK, people skilled in prior art are often called into courts in order to arrive at the decision.
Well, yes, but they're typically experts from both sides whose goal is to promote their side's case, not accurately inform the jury. That's different from a jury having a direct understanding of the practitioners point-of-view.
> While I am still trying to understand what you mean, I do not yet see a connection of this to the anti-software patents view.
I'm saying that actual practitioners are likely (and, in my view, correctly) to see more things as obvious, fewer things as novel and so on than a layperson or a patent lawyer. The impact on patent lawsuits should be obvious.
