Did they cast Remove Curse? Because my first instinct would be that, without that spell being cast, the item invariably comes back to "haunt" the person it initially cursed (providing it did curse a body.)
1. A Good church might buy it in order to destroy it. A Wizard might want it as a component for other magical rituals or if s/he could tear it down somehow. An especially arrogant noble might want it to display on the wall to show his or her fellows how "brave" he is. Apart from that, even "Evil" characters would be affected by a curse, so they'd generally avoid it unless it specifically states that a certain alignment derives benefits.
2. At a minimum (and this is something I forgot to do when I was running), it should be half of what would normally be gotten for a magic item. For example, if PCs sell for 50%, this thing should - at a minimum - be worth only 25%. Reduce that even further if its an especially virulent curse. Wouldn't it be amusing if the PCs ended having to pay to get rid of it?
3. Depends on what happens to it. If they sell (or donate) it to the Church of Awesomely Goodness which destroys it in a public ceremony celebrate Awesomely Goodness, I'd say there should be some positive implications. If, however, they sell it to a seedy looking merchant in the back alley, then have this lead into an adventure where they have to make good what they screwed up. Selling a Cursed Sword of Berserking? Guess what? In the Hamlet of Nowhereville, one of the militia bought it and then killed everyone in the Hamlet when he inevitably failed his Will save.