1:We can tell hpow many are needed by how many are ordered, or by how many generally get used.
A dubious feedback loop at best. The amount ordered could remain high, whilst more 'needy' products are pushed out. Imagine a luxury repeatedly ordered by 50% of the population against a medicine more needed by the other 50%. The order feedback loop would need to be scrutinized daily and such 'imabalances' duly debated and 'rectified' (which could mean left alone if sufficient votes go that way) likewise.
The problem with a democratic ordering system is that its as open to the well meaning abuses (eg "lets have more fireplaces built - even though it means less resources for housing) or malicious abuses (eg an influential minority ordering more of one thing without caring what that will do to others, and creating a rift)
2:If they are a specially good lamp-shade maker, why shouldn't they go on making lampshades, to order, if they run out of orders, they can find something else to do to kill the time...gardens need weeding tha knowest...lack of orders means boredom for our lamp-shade maker.
The lampshade maker doesnt require orders to live, he doesnt get traded value he gets a share of all produce - the only motivation for him to stop is his personal desire to change, which I suggest is less powerful than impending failure. But lets be reasonable and assume the lampshade man moves on to make curtians or something more useful.
: If people think they're being a wanker, they'll say so to their face.
This might change nothing.
: the point is, capitalism can't knock off when demand slumps, it has to keep on trying to produce
Business can, must and do change what they produce precisely because they face failure. I imagnienmany a lampshade factory has chnaged production to curtians. This is a more powerful feedback loop.
: Ah, I think I miss-understood your half-hour musicians
ok, I did mean lesss than productive members of a commune
: these musicians would have to note that their falling down on the job, and would have to realise that the entire system is endangered if them as are doing harder work start to feel like they need more goods. 'From each according to their abilities...' etc.
The problem being that they dont face failure in the short term, that their existence doesnt bear direct relation to their effort. In the lampshade example the commune might not change until alot of resource is wasted, in the malicious musisican (try saying that when youre drunk!) example they might not care to understand.
: their self interest does not lie in expropriation of others' work.
Their self interest cannot be decided by others, its what they decide - even if its demonstrably objectively not in their self interest - they still decide themselves. And they might not get bored.
: if the lamp-shade making were a serious drain on resources, the community would have to cut off supplying the lamp-shade maker with materials- as a last resort. People have to actively apply themselves to making teh system work.
And this is what would have to happen - people would need to be excluded from participating in the usage of community resources because people in the community would have neither the capacity or will to carry non-contributors they do not value. More over there would be disagreement about who can be carried - one could start to have unilateral withholding of produce ("Im not feeding those people, they do nothing" vs "ah, but lets give them a chance" vs "not with food which should be going to these children instead" etc etc). In other words a community can suffer from partial or full breakdown in unity following even mildly disruptive drains on their capacity and produce.
The breakdown you say must be avoided is, in my strong opinion, not really avoidable precisely because peoples goals are so diverse, and their self interest is up to them, its unrealistic to expect their chosen self interest to intersect with their demonstrable 'objective' self interest throughout each community member.
: People are ready for it, they just have to want it.
People are ready for many things they dont want. People are ready for capitalo-anarchisto-individualitio-friendly-charitable-niceism (i think i mentioned that i dont really like the moniker 'anarcho-capitalism') but clearly insufficient numbers want that to happen.