Some people create accounts in StackExchange just to put a single question and finally when they get the answer just leave the site at-least without accepting the answer as correct one. This won't encourage people to answer for the questions of others. How to avoid this? Are there better solutions to manage them properly?
This is an issue of all SE websites in general and can't be worked around.
At least think that you are answering the question of not a particular user but a Magento question in general. If the question is interesting or you just know the answer why not just answering it? After all we are all doing it not for virtual points or acceptance. Think that your answer may be useful for other people who will google the question later.