Guess what genius? The boss keeps his bottled water in that fridge too. I bet he was REALLY impressed by you when he saw this...as he was walking by the breakroom with his important potential new client that he was trying to impress.
Don't get me wrong, I'm not the straight-laced, uptight type, and I appreciate a good office prank as much as the next guy. It is important to keep in mind, that your intended audience isn't necessarily the only person that becomes an audience to communications posted throughout the office. So stop posting nasty notes about leaving the copy machine jammed, missing sandwhiches, and messy microwaves, and find a more productive professional way to fix the problems.
Innovators get promotions - duh!