Yep, and if you issue the wrong number, your company is legally obligated to issue a correction, done in an 8-K usually I believe. And this is very much frowned upon by investors (not the correction, but making the mistake in the first place).
How does investors dissatisfaction with a company making such mistake manifest itself? I assume they won't divest just for the sake of punishing the board.
Future investors would avoid the company?
Quite a few of board members are the investors, if I understand it correctly. As for how their dissatisfaction could manifest, they could vote the CEO out and put someone else in that position who will revert that level openness instantly.
They may not simply for punishment but because they lost trust in the company's ability to accurately report financials (depends on discrepancy in financials, # of misreports, etc)