Not sure if its technology or the go-to-market strategy that made these companies wildly successful:
The founder (forgot her name) realized that if she was able to vertically penetrate the market at BYU, then it would enable her horizontal growth. The students there have the influence to grow to other markets through word of mouth.
Founders want to solve problem of finding boyfriend/girlfriend, so maybe they go into their friend groups and try matching people together with similar interests.
The founders literally asked strangers to rent out rooms and offered them to other strangers that needed a place to sleep.
They basically started advertising on Craigslist to a specific region.
Starting with their own fleet of drivers to give people rides (problem = finding a ride), and eventually scaling to the point where they can hire drivers through the app.
The early Reddit team created fake profiles to post contents on the site for several months constantly. This approach made Reddit seem to have a lot of active users sharing links, which was enough to attract actual users and pushed Reddit's early growth.
To increase visibility, the Reddit founders spent $500 on stickers. These stickers were posted in publicly visible areas around Boston, Massachusetts.
The second growth hack of the team was seeding the site with quality contents by themselves (from both their real accounts and fake ones). That solved a "chicken-egg" problem, attracted more people to join the site and made Google Search - the primary traffic source for Quora even by nowadays.
De-facto, they have been selling not software, but “better, more successful teams.” After much discussion regarding Slack’s core features, the team finally decided to focus on search, leave-state synchronization, and file sharing. While not exactly flashy, these features made up Slack’s core functionality in a way that made sense to initial users and was pleasing for those who use the app all day.
Tldr: They got 10 companies to try out the IRC software internally. The founder was already an entrepreneur and well-known so word of mouth picked up quickly.
Back to Tinder:
To solve the early chicken-egg problem they sent their pitch-team ("pretty/cool/successful women") all over the country to pitch Tinder to college sororities and make all the cool girls at the meetings install the app (to provide the "supply"). Then the pitch-team went to the corresponding brother fraternity - guys opened the app and saw all these cute girls they knew.
2013 Tinder shifted its marketing tactics to "city by city" technique to begin expansion into the 25-34 demographic. Tinder conducted launch parties with the requirement to display the installed app on a mobile to gain admission to the party.
"No Ads! No Games! No Gimmicks" - became a famous growth hack WhatsApp utilized to leverage their growth since. WhatsApp was not the developer of the only app that took the opportunity of Apple's push notification.
The company had Community Managers in a variety of locations in San Francisco whose job was to promote Yelp and grow the Yelp community in their hometown. Yelp augmented this core content with their own, launching local blogs, city pages, user-generated lists and other content all aimed at reaching more users through search.