Answer:
One problem is that appeasement never ends. For example, when Neville Chamberlain decided to appease Adolph Hitler, the idea was that it would lead to peace because Hitler would (supposedly) be satisfied with the compromise that had been offered to him. But as we know, Hitler was far from satisfied. And that is what often happens: the person (or persons) being appeased usually decide they want more. Appeasement is often seen as a sign of weakness, and it seldom gets the desired result, since the stronger party will usually come back to the weaker one with even more demands.