(This picture, from CBS, shows the world record-breaking card house, from Bryan Berg, of the Venetian Casino. The man who controls the Venetian empire, Sheldon Adelson, formerly ran the Comdex computer shows.)
It's inherently fragile. For any software program to work it must be perfect, or it collapses. The larger the system, the harder this is to maintain.
Then there is the fact that you have all sorts of people trying to blow holes in it all the time -- the number and tenacity of such people increases as the software becomes more critical.
The difference between "open" and "closed" software is mainly a legal one. You can see and edit Microsoft code. Criminals do it all the time. Both open and closed source are equally vulnerable.
But most people are not criminals. Most people are good. Most people even follow EULAs, that's how good they are. This is the social reason why open source works. Both types of software have people trying to blow holes through them. But open source can bring more resources to bear in fixing them.
Anyone who has tried to build a large, proprietary system from scratch knows how hard it is. It gets exponentially harder as the system scales. You might call it Moore's Law of Software Degradation. Bigger stacks mean more things can go wrong.
Thus we have Steve Jobs' secret source. Every once in a while he drops what he built before and starts again from scratch. The Mac OSX is large, but based on an open source
LinuxUnix, so it can maintain. The iOS is new, and relatively small -- everything old becomes new again.
Innovation can happen within smaller systems. The houses are smaller. They can be built by small teams. So throughout my 30 year career I've watched constant reiterations of the same old things. Web games of the '90s copied PC games of the '80s. Phone games of the '00s were the same. Apps, again, mostly, the same. Only the displays get better.
As a system gets bigger the need for an open source process grows, the need to cooperate grows if this skyscraper of cards is to keep standing and growing.
That's why Mozilla joined the Open Invention Network -- to protect its growing code base. It's also why the Bilski case matters little in the end -- the incentive for people to cooperate despite patents is too great.
Once you understand that all software is a house of cards, subject to Moore's Law of Software Degradation, the need for open source becomes clear.
If it didn't exist we'd have to invent it.