Schneier's original point is "every cooperative system will always contain parasitic elements; while these elements can be deleterious to the correct functioning of the system, they are also a critically important source of diversity and change."
If all the reader gets out of the article is that "systems never perform at 100% efficiency" then they are ignoring the entire point of the article. As such, the root post seems to be hijacking the topic rather than talking about what Schneier actually said.
1) In any system of nominally co-operative elements, with ability for individual elements to flip between co-operating or defecting (to use the same game theory terms Schneir did) will have some fraction of those elements in 'defecting' mode.
2) He accepts as fact that perfect control over the choice of defecting or co-operating is impossible to achieve in the systems he's talking about.
3) He outlines a way to reason about the processes and measurements one can put into a system which maximizes for 'cooperation'.
Then Schneir applies this very good and universal tenet toward security. and finally points out that even if systems could achieve perfect control that would be net negative as the 'defectors' in the system can provide the mutation/change which improves the system overall.
It is a solid piece of reasoning which, in my opinon, applies to all systems, not just security systems. Systems that include groups of people, computer networks, air traffic control, commodity markets, Etc. All of them.
Take a Gaussian distribution and point at one of the wings and there be the 'dishonest minority' there. If you are a designing a system where the actors (or agents) in your system have the freedom to choose their own path through it, whether it is an MMORPG or a botnet or a homeless shelter, you have to consider (and prepare for) the fact that a portion of your system's population will be working against the system as a whole and if you don't want the whole system to collapse you need to heed Schneir's advice and layer in processes which 'self heal' or 'detect and deter' such defections. Otherwise your system will become unstable, and then collapse.
It seems like the point the OP was driving at is that Schneier's statement is a subset of that maxim. While Schneier's point is certainly important, the generalized form of "systems are not perfect, work with it" is more widely applicable. He wasn't ignoring what Schneier said, but agreeing with and building on it.
The poor are a parasitic element, if we're talking about the same "poor". I'm not talking about the hard-working folks who bring in a crappy wage because their skillset sucks, I'm talking about the folks who have decided that it's a better idea just to stand on a street corner with their hand out hoping to take advantage of the compassion of others.
If by poor you mean lazy, then say lazy. Right now you are poor in karma because you were too lazy to articulate your idea more clearly, and have obviously offended several people enough to get downvoted. I wasn't one of them, but statements like 'the poor are a parasitic element' are pointlessly antagonistic.
While I'd clearly be wrong to state that there are no such people, I think it's important to note that even most people with the signs asking for money aren't doing so by choice. Once you're in a state where you really do need to beg for money for basic sustenance as such (which can happen surprisingly easily through no real fault of your own), it's really, really hard to get out, no matter how hard you try. And, in the meantime, while you are working to get out of it, you have to do something to live.
There is some (insufficient, at least in the US) help available from government programs and whatnot, but even non-participation in such things is not always necessarily by choice.
I've known a fair number of people who've worked their way out of poverty (my family among them), and I've known a larger number who have failed to do so by no real fault of their own. Your unkind generalisations are most definitely unwelcome.
