At the PHPCon 2002 that happened just a little while back, there were tons of presentations, including one from a Yahoo! engineer and their local MySQL advocate, Jeremy Zawodny. Now, I know what you're thinking - and no, this isn't the same one as before. This presentation covers a different topic - Scaling in MySQL and PHP

From these slides you can get a good idea of what he covered in his talk. It's an interesting story of how they implemented MySQL and PHP on remember.yahoo.com (tribute to the 9.11 happenings). The basic concept was that anyone could make these "tiles" for the system, that included text, canned images and custom text to it, then allowed them to share it with the world. While human intervention played a large part in the success of this project, they also saw PHP and MySQL fall a little bit short of what they expected - due to their database design and code structure, not the limitations of the language.

Thanks to Ewald for the link...