When I was at university studying CS I was running a Arduino fansite and a fansite for a videogame - both of whom made most of their money from affiliate revenue (a couple hundred bucks per month).
I thought it would be cool to work at Reddit (was close to graduating), and I had read blog posts from here and various other sites and IRC about how hiring managers liked projects.
I took to it to build a JS library that converted links to affiliate links, for example amazon and some other small retailers I had used.
Basically you just parse any URL you embed in the page with this library and it would convert the existing (non-affiliate) links to affiliate links with your signature attached so you got a revenue share.
In addition to this, I had done research on Reddit's traffics and crawled reddit to see how many affiliate-capable links existed. I talked about this in the interview and suggested they could make around 2 million per month if they hired me and used my script.
--> I was rejected after the interview, but a couple months later Reddit announced it was experimenting with a new feature that would re-write links as affiliate. They ended up implementing this feature that I am 95% sure I came up with and someone else stole.
It was one of the shittiest experiences I have ever had interviewing, especially since I didn't get a job out of it but I believe they have made millions off of this idea so far.
I huge put off, but I've learned since then backstabbing and stealing ideas is a big part of politics in most corporations. What a bummer.