Ok, I just had to laugh. The Oracle FAQ site OraFAQ runs on... MySQL! I guess it just goes to show how cost-effective open source is. Here's some quotes from a thread on their discussion forum:
"Interesting - we don't run an Oracle database. But I suppose we ARE a free site so are probably a bit short of cash.
"What cash? Every penny we make goes back into running and developing this site. There is no way we would be able to raise the money required to buy a commercial Oracle license.
To be honest, it's not a surprise. There are tens of thousands of web sites that run MySQL ranging from the mega sites like Yahoo, Google, Craigslist, Travelocity, to many ecommerce sites, blogs, forums, and discussion sites. After all, the price is right and there's no hidden "bait and switch" pricing when you hit a couple of gigs of memory. So guys, keep on using MySQL!
- OraFAQ: Runs on MySQL