Grass roots initiatives are naturally appealing to anarchists and all lovers of freedom. They are great for getting things done that people mostly already know how to do. But if a project requires a high level of expertise, and a complicated level of coordination of many people, another approach is needed. A combination of a hierarchical system and a grass roots system may be more appropriate. Information can flow in both directions: from one (or few) top coordinating person(s) to many experts and from the experts back up to the coordinator(s).
A grass roots approach to culture change is somewhat like a "random walk" or diffusion in physical systems, or random mutations in biological systems. It takes longer to find the mountain pass with a random walk than if one is able to see the fitness landscape and the direction of the pass and head that way. This is a kind of conscious speciation, where a master meme (the direction of the pass) is identified and then selected for consciously, not by natural selection (which would select against it before it made it through the pass). Natural selection/genetic algorithm/random walk/diffusion would eventually work, but it might take too long, unless the fitness landscape changes significantly so that the fitness or entropic barrier becomes small.
To bring it back to concrete reality: The culture of empire is not going to change by grass root approaches unless something drastic happens (economic, political or ecological collapse, or a slow decline of industrial civilization due to peak oil or such). If industrial technology and capitalism are master memes, then changing them in a small, coordinated group with the help of expert craftspeople and farmers is a more pragmatic and quicker approach then letting a craft/agrarian based technology evolve by a grass roots approach (what the Possibility Alliance is doing). Hence the Luddite Manhattan Project. Imagine trying to build the atom bomb with a grass roots approach--it won't work. A craft/agrarian-based technology and a gift economy are even more complicated tasks (more memes are involved that need to be coordinated in a network). That kind of technology evolved from earlier technologies over many generations because there was a path almost always going downhill, but the path to it from where we are now has a large fitness barrier. No single farmer or craftsperson can get there.
The problem right now is to convey the meme of creating a local technology ecosystem. It is too much for most people to understand this--crafts are for art and luxuries and technology is magic and not to be tampered with in any drastic way in most people's minds. Rather than understanding it, it might be possible to pay some expert craftpeople (not tradespeople, like plumbers, electricians, builders, etc. since these are too tied to the current industrial production) and farmers to just figure out what they need in order to produce what someone else needs and enlist the help of a computer program to do the necessary computations and display the missing links. Some pre-industrial crafts do not have any more living practitioners (e.g. coopering in certain places). Most people have no knowledge of these crafts. The few pre-industrial craftspeople that exist can't make a living because they don't have a supporting infrastructure (other craftspeople and farmers), except making foo-foo artsy stuff for wealthy people. Also, they are using much industrial infrastructure in their craft because it is more readily available. To create a local technology infrastructure is a challenging networking problem.
There are those, like Charles Eisenstein, who think that the whole technological question can be bypassed with economics. But technology underlies economics. A global, centralized technology that devalues human craftsmanship, nature, relationships and creative work will create a global economy with the same values, even if the values that people want are different. We can give lip service to a gift economy, but our technology does not support it. In the production (less so in the consumption) of the goods we need to live, we produce slavery, war, toxic waste, alienation, a gross misuse of human creativity, destruction of nature.