While you may not have a right to tell the companies you fund what to do, you certainly have the right not to fund them. At the same time, you are running a for

While you may not have a right to tell the companies you fund what to do, you certainly have the right not to fund them. At the same time, you are running a for-profit business, and turning down a company you feel is likely to be successful isn't responsible to the other people involved in Y Combinator. And as far as I know, they could have entered the program with a different product and changed tacks partway through. All this to say that I do not have the right nor the information to question your professional decisions. Personally, though... is this a product you're proud of?