People have occupied Shell offices in solidarity with the Ogoni people of Nigeria, trashed fields of GM crops, and hung banners from Nestle offices, working in 'affinity groups', built on mutual trust between a handful of people. Many volunteer co-ordinators would be shocked if they saw how these groups work internally. It's sometimes referred to as 'disorganisation'. In some ways it's volunteering in its purest form. People freely take on tasks simply because they need undertaking.
Hierarchy is shunned, with consensus being the main decision-making mecahnism.
Often meetings are dull and even tortuous, but any suggestion of the creation of a bureaucratic structure, with membership and leaders, is fiercely attacked. Volunteering is often portrayed as the sign of a healthy civil society, and a great contributor to democracy. One of the main accusations levelled against direct action groups is that they are anti-democratic, seeking to impose their will rather than using the democratic system to have their say. This is a persuasive argument, but could equally be levelled at any interest group. Most protesters would argue that in a society with huge imbalances of power and wealth, democracy is almost meaningless.