I recall hearing a stat at Yahoo orientation in 2004 that a very large % of Yahoo accounts had the zip code as 90210. I can't remember what it was, but I want to say something like 5-10%. Dramatically larger than any zip code could legitimately have.
My personal favorite was Tommy Tutone and the number I used was 8675309 with a zip code of 90210.
Lasted for a year and then they deleted it.
I'm a little less flippant now.