Image psychological affect

[bone77]

Why exactly would you not want your opponent(s) to bluff at you? This is where the psychology of the game comes into play, being able to recognize their bluffs. What happens when you're at a table full of unknows, be it online or B&M and they don't know your rock-like status, do you tell the whole table when you start that you're a rock? It seems to me that you're missing out on a lot of things, most noticeably pots and extra bets when either you opponent successfully bluffs you out of a pot (after all you believe that he would not bluff you), or when they would make a desperation bet/bluff on the river and you snap it off.
What do you think?