I have long admired the sterling work of Diabetes UK in engaging their members in advocacy to raise awareness and funds.
As the quote below emphasizes, members (or customers for that matter) have a pivotal role as ambassadors, advocates and promoters of your cause and brand. Diabetes UK has been very effective creating a voice.
“Many charities go out and just ask people for money; We ask people for their voice”. Scott Harrison CEO, charity: water speaking at Inbound2013