I actually do this where I answer the question with the correct answer plain and simple and then go in and type up more stuff at a later time, as I think of more stuff to add in order to provide a more helpful answer to the person.
An example is this question http://pokemondb.net/pokebase/85578/what-pokemon-has-the-highest-attack-in-ru
, where I answered Archeops and Escavalier at first, then edited to provde the NU Pokemon.
I don't see any problems with this, I answer first and I answer with correct information. That alone should give me the best answer. Anything I add on after that provides additional help to the people.
Just an example of how this is not always some evil scheme for points, just searching for more info to add to provide a better answer.
I would like to say though that if your answer is not correct in the first place, you should hide your answer when proving wrong instead of just editing to the correct answer.
If you're going to do something like this, make sure you have the correct answer before adding more information. And make sure the info is not just copying text from a link that was posted in another answer.