Every day I see search referers for questions to which I know the answer. Sometimes an article of mine will be a perfect match, and I feel like I've done someone a service, but often a search seems to have matched across multiple articles or partially on my link list or whatever. I've not specifically written about the combinations (interactions?) of topics the searcher wants, but I still know the answers.
I may start picking hot search topics from my referer list and post answers just to those searches. Unfortunately, I'll not be able to contact the original searcher, but maybe it'll help the next person.