Don’t use the -server or -daemon switch or run bitcoind on a machine where you use a web browser. It opens port 8332 on 127.0.0.1, the local loopback address, and you wouldn’t think that web browsers could cross-site access it, but it is possible.
This sounds like something I would not like to have happen, but what does it mean? Let’s face it, we’re ALL generating Bitcoins on everything we can get hold of. What is the potential damage, in language my Mom might understand?