Part of the problem is that Twitter encouraged automated signups in the early days, blazing the trail for gigantic bot-farms that we all talk about today. They

Part of the problem is that Twitter encouraged automated signups in the early days, blazing the trail for gigantic bot-farms that we all talk about today. They pushed popular rss-to-tweet gateways, wordpress plugins for auto-tweeting blog posts, etc. There should have been gigantic red flags waving when the hypergrowth of Twitter really started, because you knew these weren't all people signing up for one account. I'm not sure if Twitter can ever put pandora back in the box, but at the very least, requiring a mobile number is a start. It's hard(-ish) to generate thousands of bots if you have to have a unique phone number with multifactor for each signup.