I thought it meant something more along the lines of you did something nice for me, so I'll do something nice for you.
Personally, I think the aforementioned proverb is rather self-centered, in that ultimately it focuses on motivation rather than the ecological preservation of those around you. Though, if taken in a different matter, it is intuitive─one who has been done better can serve one's community more effectively than one who has not.
Perhaps, and yet it might be very old, from a culture in which such thinking was standard, say, the ancient Greeks. Indeed, from its formulation, it may come from one of Aisop's fables. I'm not sure, but it seems to echo similar sentiments. See, we tend to believe, for the most part, that one should not go eye for an eye. Yet to the Greeks a person was best if they were good to their friends, and wicked to their enemies. This concept of reciprocal action was very prevalent, even in their relations with their gods. As many other ancient religions, it was very much a 'I do this for you, so you should do this for me' sort of relationship. So I think Thought is right regarding the intent of the proverb. It's just saying 'if someone's done something nice for you, you should be nice back.'
