Some of the implications of overpaying for an acquired company are when stock prices are affected. If a company chooses to make a deal and stock prices are declined, that usually is a hint that a company overpaid to close a deal. If a company finds themselves in a position that the deal is being prolonged and the amount is drastically surpassing what initial their goal amount is usually a sign that the company is overpaying.
Yes stock price decline is certainly one implication and it happens often. Can you think of any others?