Actually, the circumstances requiring a new nickname were kind of scary. I tend to use one nickname for everything, so I had this really cute variant of my real name as my standard nickname. One night, on AIM, I received a random IM from a guy wanting to talk. I ignored him and he kept bugging me. Finally, I asked him to leave me alone and he tells me that the last person who told him that, he tracked down and raped. He told me that he had linked to my LiveJournal and was reading about me. While I didn't post enough information for him to figure out who I was, he could narrow it down to my campus and department pretty fast.
While I was pretty sure it was a sick joke, I wasn't taking any chances. I closed the AIM account, blog, etc. However, my friends and I used them to keep in touch, so I had to come up with something new really quickly. I figured... well, I'm a chemist. "Bad" can either mean fabulous or just plain bad. In my work, I've had moments of utter brilliance and utter stupidity, so I figured "thebadchemist" kind of sums me up pretty well. Nowadays, I just worry that I might post a story on here and someone I know might recognize it!