I thought about responding in private but I feel this is a good topic to discuss in the open. While I don't particularity care for someone posting only once with a question and once they see their answer never post up at least a thank you, I am not sure making it a rule that you have to introduce yourself is such a good idea. At one time I strongly shared the belief that one should but now feel it might drive potential members off when we say you must say hi or tell us about yourself. You know how it is at times, you run into a problem and start searching online for a solution. Who wants to introduce their-selves? On the flip side of that coin I think it is respectful to be polite and not use forums just to get what you want and give nothing back.
What changed my mind on the matter was why do we need someone to say hi that has a legitimate question to which we can give a good answer? I don't do this as a matter of pride, I just want to help others and in turn be helped. At the end of the day the OP might not respond back in thanks but I guarantee there will be lurkers who might read and learn from our answers, which is a win in my book.
And, it does sound a little snobbish, and I'm guilty of doing it, to answer someones first question with something like "I have your answer but first tell me about yourself" or something to that nature. True, we are a very close "family" but that won't change with the 1% of posters who never come back and post again.
Just a few thoughts.