What were the underlying themes at Cannes Lions 2015? From encouraging people to improve themselves through the power of shame to enabling people to improve the world through digital channels, many of this year's winners set out to encourage positive behaviour change.

From Just Giving Facebook updates to wearing H&M’s Conscious Collection, public displays of philanthropy have become a symbol of status. But does it really matter that these new do-gooders are motivated only by people seeing them do good if the outcome is still positive?

In December 2013, the law allowing gay marriage was overturned in Australia – spurring outrage, as two thirds of people support same-sex unions. At Sydney's Mardi Gras, ANZ turned its cashpoints into glitzy GAYTMs, sending a bold statement: accept our cash, accept our values.

Public shaming is back on the agenda. From fears of being photographed eating on the tube, to apps that erase pics from the night before – the spectre of public criticism looms large. Has social media revived this age-old mechanism of control? Or can shame be a force for positive change?