19. A specialized search engine for discussions
Discussions a better source for the truth than professional clickbait articles which dominate Google search results.
Problem
You want to buy a set of headphones, so you Google for reviews. The top results are all “Top 5 Best Headphones of 2022” as well as clickbait articles that have good SEO. So you add `site:reddit.com` to your query, which gets you a lot closer.
You don’t use Reddit’s own search as it is notoriously bad for actually finding anything. Also: there’s more than just Reddit, perhaps an audiophile forum you have never heard of would be a good source too.
Solution
A search engine that only seeks to index discussions and other user generated content.
Google was originally built around the idea that pages that have links from authorative websites, which themselves are linked to a lot, score higher (with an algorithm PageRank: was it named after Larry Page or the fact that it ranks pages?).
Over time this system was no longer enough, to the point that Google uses a huge mixture of signals to rank pages, which spawned a new industry full of SEO (Search Engine Optimization) experts who claim to understand how to rank highly on the web.
Discussions and other social media have a different structure though than most pages, most often there are almost no links pointing towards good discussions. Instead a discussion thread as well as individual posts may have some sort of rating (upvotes), enagement, and controversialness. Also users may have different levels of authority (e.g. measured by how old their account is).
Motivation
Building a competitor to Google Search is an impossible task: there is an incredibly long tail of content which makes building an all-purpose internet search engine near impossible. What’s more: people have an incentive to play the system (SEO).
By picking a subset of queries as well as sources (one could start by only supporting Reddit) one can do a better job than Google.
Business Model
Many users will use this search engine for searching for product reviews: if you detect such a query you should perhaps display direct links to where said product can be bought (fetching an affiliate fee). Alternatively the data of who searches for what can be offered as a paid API.
Plain old ads are of course also an option.
When you end up building a specialized search engine that in itself is valuable technology that may one day be licensable (or acqui-hirable) to social media companies.