Whenever there's a junker on the board, I will over-buy it to excess and build a deck around playing them as quickly as possible. Less because I think cursing itself is good, but more because I hate dealing with deck junking. After all, you don't have to worry about curses if you opponent has all 10 of them.
(Oh, and if there is rats + any trash-for-benefit on the board, I will buy rats. There is no exceptions to this rule. Anybody who forgoes rats in a set where rats can be used will be silently but sternly disapproved of. Cowards.)