To be honest, if the reward outweighed the risk, then I would buy Poacher's Knife.
Like 5X the gold might make it playable. You get caught out in the enemy jungle? Doesn't matter, you as much, if not more gold, from the camp you stole (eventually more because of death bounties) and the enemy jungler is down a camp. You don't get punished? You win the game because of how much gold you get to snowball the game. Of course it would probably be snowbally as hell and still has the problem of the opposing team knowing that you are going to be counterjungling.
Of course, telegraphing your gameplan is but one of many problems that Poacher's Knife has. Other problems Poacher's has include, but are not limited to:
-It's useless if you are behind. Stalker's and Skirmisher's both give extra combat presence, while Ranger's gives extra sustain so you can impact the map more and waveclear when you need it. Poacher's does nothing on your own jungle creeps and does nothing to enemy champions.
-It's not as useful when you are ahead. Stalker's and Skirmisher's give extra combat presence to snowball leads, Ranger's gives extra sustain to push for objectives or kills farther, but being ahead means that the enemy jungle is at the mercy of your entire team, and you are not guaranteed to get value out of Poacher's Knife.
I probably missed a few reasons (there are a whole lot more reasons to not get Poacher's Knife, but I can't think of a whole lot more that haven't been mentioned), but these two reasons and it telegraphing how you are going to play the game are to two biggest issues with the item.