Cafe TC, a popular nightspot in New Delhi, had a makeover. But not a lot of money to tell people about that. They wanted to reach the hippest of the hip where they hang on WhatsApp but WhatsApp doesn't allow spam or ads. At least not in the form of banner ads. They do allow brands to be on WhatsApp, with the theory being you have to opt-in to follow them. But just to make sure their message was seen, they created a special custom API that made their message blink, just like a ticker. The results were impressive with loads of people wanting to get in on the party.
For other examples of brands using WhatsApp, check out the Clark's shoes Rats to Rudeboys campaign from earlier this year. Absolut in Argentina was the first brand to use WhatsApp for its launch party back in 2013. As for WhatsApp's "No advertising policy," obviously these ads demonstrate the contrary. But it's also important to note, Facebook, which is littered with ads, owns WhatsApp, paying a staggering 22 billion for the service last year. So it's not like they're making a sacrifice or taking a big stance.