(Not a commercial plug - just a wasy of identifyign the book ...)
Many current social movements, I would argue, are a removal of legitimation by large sectors of the populations, because they Governments are not doing what their people want.
I do wonder if Legitimation Crisis might be appropriate for the Globalization and New World Order. Facebook and other social media have widened the discussion and widened people's views - and they do not accept it - so they are removing legitimization.
Inequality in terms of economic , political, social and symbolic resources is the major cause of political unrest. Political unrest can also come up because of regional inequality. This is a difficult question to answer when asked in abstraction. The context of any political and social movement matters. Political theory since the time of Aristotle has answered that inequality of various types can be potential source for political and social movements.
As Dr. Vaddiraju implies, above, this is a difficult question to answer in the abstract, in a short answer venue such as this, because there is an entire body of research which has been done on why people take collective action, and what allows collective action to arise. Dr. Vaddiraju is also correct that inequality is a major contributor to the emergence of the social and political environment which facilitates the rise of social movements.
For a comprehensive answer to your question, I highly recommend _Readings on Social Movements: Origins Dynamics and Outcomes_ by Doug McAdam and David A. Snow. In covering the question of how social movements emerge, McAdam and Snow (2010) posit that the emergence of social movements occurs when there are sufficient disruptions to the "quotidian," or daily life of the people (Snow, Cress, Downey and Jones 1998), sufficient breakdown of the state (Goldstone 1991), or sufficient social change to create a sense threat, or of anomie (Dyke and Soule 2002). In other words, social movements form when people experience sufficient social disruption or sense of threat, especially to their daily life, that they simply can't continue to *NOT* do something. Essentially, most people tend to simply go along with their daily lives until something disrupts those lives sufficiently that they feel a need to respond, and when this happens on a sufficient level (which is relative for each individual), they look to respond. When this disruption expands from the personal to the social level, people respond collectively.
All of the articles listed after McAdam and Snow are actually listed in the first chapter of McAdam and Snow, so you can get all of those articles and more from McAdam and Snow, which is a reader used as a textbook in teaching Social Movements here in the U.S.