Society at the most basic level exists to stop humans from having to spend all their time being concerned with basic needs like water and food, shelter, and protection, never mind having a stable enough environment to raise children. Nanotech looks as though it will affect all these, both in a positive and negative way.
Society currently depends on most of the people, most of the time, following the rules and agreements that make society function. For a simple example of this look at driving on the roads. Most rules are only enforced by there being consequences if they are broken. Nanotech makes it possible to check that rules are being followed, and immediately enforce the consequences of broken agreements.
Human society is affected by the desire of most humans to be in regular contact with other humans, preferably those that they are familar with (sometimes described as the "herding instinct"). The majority of humans have a respect for authority and hierarchy (referred to as "pecking order"), and this tends to affect the social structures that they are most happy with.
The development of society seems have started with groups of extended families with a common culture, or "tribes". These may be more or less considerate of other tribes, in the most extreme cases considering them to not be human, and hence having any human rights, with any level of violence being acceptable against them. Even in non-tribal societies followers of religions, team sports, criminals, or particular political systems, may follow tribal beliefs. Nanotech in the hands of such people needs to be carefully considered.
Civilization considers that there are ethics which apply to all people, without exception. This may include respect for other's beliefs, an understanding that others will have different priorities, that considerable efforts should be made to allow those who break rules and agreements to continue to take some part in society, that the current and future living environment needs to be considered, and that there needs to be a mechanism with checks and balances that can change society to meet changing circumstances. This is just a 'humane' set of ethics, there are many others which can make up a working civilization.
Most of the time most people don't have the resources to consider whether society is working properly or whether they need to do something to fix things. Currently we delegate this work to specialists, like philosophers, politicians or religious leaders. We then have the problem as to whether they are doing their job properly, given their human limitations. Nanotech has the potential to freeze the structures of society in ways that could be very dangerous in the longer term, or make society so fluid that no human can grasp how or why it is changing.
Decisions about nanotech have the potential to interact in ways that are very difficult to predict with all of the above.
This post was made to sci.nanotech, but not accepted, probably as it was considered to be too far Off Topic. However, many of the discussions in the sci.nanotech newsgroup have implied a consideration of the above, but may well have been based on differing assumptions.
(c) Rory O. McLean, 1980 - Feb. 2006 Permission granted to use for non-profit making purposes