This was back in 2012. There have been many more since and will be many more in future. From The Upstarts, by Brad Stone, loc 2871-2887:
But Uber was going to need more than Tweets to sway the DC city council. First, colleagues remember, Kalanick sought the backing of the DC tech community and tried to enlist the support of the online-deals company Living Social, based in Virginia. When they didn’t respond, Kalanick decided to go right to his customer base. He sent an impassioned letter to thousands of Uber users in DC, complaining that the city council would make it impossible for the company to lower fares and ensure reliable service. “The goal [of the Uber amendments] is essentially to protect a taxi industry that has significant experience in influencing local politicians,” he wrote, basically accusing Cheh and her colleagues of corruption. 16 Then he supplied the phone numbers, e-mail addresses, and Twitter handles of all twelve members of the DC city council and urged his customers to make their voices heard. The next day he posted a public letter to the council members, writing ominously, “Why would you so clearly put a special interest ahead of the interests of those who elected you? The nation’s eyes are watching to see what DC’s elected officials stand for.” Mary Cheh was taken aback by the ferocity of the response. Within twenty-four hours, the council members received fifty thousand e-mails and thirty-seven thousand Tweets with the hashtag #UberDCLove. 17 When they arrived for the last session of the summer on July 10, Cheh’s colleagues all turned to her in confusion and fear. The amendments, she told me years later, had been “a toss to Jim Graham and the taxi drivers,” and now, with the weight of the internet bearing down on the council members, the amendments clearly weren’t worth it.