When I was a kid, my parents had a bunch of old SF short-story anthologies. The story I'm trying to track down was featured in one of them, but I don't remember the title, the author, or the year... (One of the collections was "SF '59: The Year's Greatest Science Fiction and Fantasy", but I have tracked down the title listing for that one and it's not the one. It would have been from approximately the same period, though.)
The story in question is not "hard" SF; it's simply set in an indeterminate near future. The protagonist is an inventor who has built "a better mousetrap" and is trying to find a buyer/investor; he's been looking a long time, and his only friend is his pet mouse who demonstrates the mousetrap for the benefit of prospects. This time, however, the prospective investor insists on absolute proof that the mousetrap is inescapable, and the protagonist finds himself watching his friend drown. (I no longer even remember whether the investor signs the deal in the end or not... it's been at least 30 years since I read it. I do remember crying my eyes out, though.)
The story came back to my mind because some friends of mine are being put through a similar ordeal by a venture capitalist; it's no longer clear whether their startup will still be recognizable as theirs if and when it gets fully funded. I just wanted to pass along the story - if I can find it - as a reminder that this sort of thing has been going on for a long time.