<< Scientists at Rensselaer Polytechnic Institute have found that when just 10 percent of the population holds an unshakable belief, their belief will always be adopted by the majority of the society.

[snip]

<< "When the number of committed opinion holders is below 10 percent, there is no visible progress in the spread of ideas. It would literally take the amount of time comparable to the age of the universe for this size group to reach the majority," said SCNARC Director Boleslaw Szymanski, the Claire and Roland Schmitt Distinguished Professor at Rensselaer. "Once that number grows above 10 percent, the idea spreads like flame." >>

Source:
http://scienceblog.com/46622/minority-rules-scientists-discover-tipping-point-for-the-spread-of-ideas/

I learned about this article at http://www.americablog.com/2011/07/science-news-tipping-point-for-ideasif.html

Important points to note are that (a) the minority must hold an unshakable belief, which would be exceedingly rare, and (b) the real battle would be getting to 10%. Nevertheless, the study should provide comfort to activists of all stripes.