Twitter expands ad offering as it faces questions over paid-for harassment

‘Objective-based’ campaigns give self-service advertisers ever more options to give Twitter money – but so do trollsTwitter is expanding its advertising offering, letting users decide to pay for their adverts based on whether or not they achieve their objectives, rather than simply paying per view. But the move comes as the company faces pressure over its self-service advertising tools, which have been used to troll and harass users of the site even after it announced a crackdown on harass