How about when you end up with a truncated last name? At this point I have to maintain a list with comments on what my last name actually ended up being in the system for each website. Especially when I have to enter my name in for password retrieval.
I at one point had a name that was extremely long. Because it was in two pieces rather than four, it was usually misspelled rather than truncated.
I don't have a terribly long name, but I still end up signing some doodle that is made up of initials.