I have a few, somewhat contradictory, thoughts: Firstly, ideas are worth nothing, and you cannot own them. Everyone has ideas, and they're all derived from th

I have a few, somewhat contradictory, thoughts: Firstly, ideas are worth nothing, and you cannot own them. Everyone has ideas, and they're all derived from the our previous experiences, conversations, reading, etc. As you say, it's not exactly what you described, so they've maybe (or maybe not) mixed some of your discussion with some other things, and here they are. Like every other startup ever. What matters is how you execute. And it appears that they're doing ok so far, enough to get into an incubator, and make a run at it. Good for them, but this is the easy part. Execution is non-stop: every day, week, month, year, you need to keep executing well. That's the real value of a startup, much more than the idea. Secondly, and kinda OTOH, if you're friends and you had a conversation in the relatively recent past in which you discussed your startup ideas, and they went off and are building something largely based on that discussion, and you weren't invited to join or even consulted, I can see why you'd feel upset. It's a shame you missed the first opportunity to say "hey, didn't we talk about this?" when you first heard about their thing, because now you're going to look like your response is calculated, rather than natural. On balance, I think it's worth talking about though, because (given your post here) it seems you will find it hard to just let it go, and so you need to resolve your relationship with these people. I think it's very unlikely that they'd say something like "oh yeah, you're right, hey -- have 25% equity and come join us", and far more likely that they get super defensive and avoid contact with you in future. Good luck!