Not having an audience or backing from an accelerator. It is amusing to see people, even on HN, get excited over a backed startup making the equivalent of half a feature in our product.
It's amusement instead of bitterness because we're already, and have always been, profitable doing machine learning projects for large organizations in different sectors and industries and we just happen to be building our machine learning platform to solve real problems we have first hand experience with. I suppose I'd feel differently if this were our "startup idea" and our success depended on that traction/audience.
However, we're always interested in people who do machine learning for a living [not just blogging/YouTubing/Mediuming/Tweeting/Audiencing about it] using our platform[0]. They may be dealing with problems we haven't seen, working on interesting projects, and it's always a blast to talk with these people.