Apparently, I was one of those people. It was at the start of a large joint project with computer science, which would focus on information retrieval -- and my thesis work would have to be one of the introductory shellings between the two departments.
Somehow, our reasoning was remarkably compatible. Some things that had caused quite a bit of discussion with his past thesis students where not an issue at all with me. In the end, I conducted an experiment that we both found interesting in the field of Information Retrieval and search engines.
He told me he would try to get funding for more experiments, but sadly enough that never materialised (I took a year-long contract with the computer science department to conduct research on documt classification algorithms to give him time to get the funds). By that time I had quite a bit of experience with IR under my belt, which enabled me to get the job at Cap Gemini, which in turn led to the formation of Semergy.
We live in the same town, so once in a while we meet on the street, but our (brief) conversations then never go beyond 'How are things?'.
Before I really started work on my thesis, we looked at Cyc -- the top X concepts had just been released, and I wrote a small browser for that, but it was too little to be of any real use.
Last week, I found an article on SlashDot about OpenCyc, the 'open source' version of Cyc, so I shot off an email alerting him about this. He mailed me back almost immediately, and asked if I was up for having a cup of coffee somewhere sometime, to catch up with each others' lives.
So this afternoon, he was here to chat about all sorts of things. It is very stimulating to talk with someone who has a lot of experience, is smart, knows a lot about all sorts of things and has broad interests. He talked about his new job (computer science teacher in Maastricht) and his plans for that. We talked about our plans for the future, and I showed him some of the contraptions we had made -- now he wants to learn microcontrollers as well. ;)
He announced he was going to leave for three times, and then we would find a new subject to talk about, delaying his departure again. To me, that is a sign that of a good conversation where every participant has something to add to the mix. That is really stimulating.
I intend to keep closer in touch with him in the future.