Many years ago I became obsessed with personal computer market share. I remember wanting desperately to argue with other geeks on the Internet about whether the Apple ][ had a greater share than the Commodore 64 or vice versa, but the problem was that nobody seemed to have this information.
One night I went into insane researching mode and stayed up until three in the morning trying to find the answers to my questions. I gathered up all the numbers, and put it on a single page, for which I did no advertising. For years it was the #1 or #2 result for Googling "personal computer market share", simply because nobody else had bothered to tally up these numbers.
You can visit the page here: http://jeremyreimer.com/postman/node/329
or read the more full-featured article I wrote for Ars Technica based on these numbers here: http://arstechnica.com/old/content/2005/12/total-share.ars
After this, I gradually lost interest in the whole concept of market share, mostly because it was (for me) a solved historical problem now, but also because I moved on to other things.
Then out of the blue I found this article that had taken my numbers, moved the whole graph to a really cool logarithmic scale, and added data for iPhones, Android phones, and iPads!
This is a really cool example of people building on top of other people’s work, without having to ask permission but being nice about attribution. It’s nice to see the data I had long forgotten about being used in new and novel ways.