Why not merge reputation across SO, SF, and SU?
It seems you need a different account on all 4 of these sites, even though the openid can be the same. You also have independent rating systems.
Why not just have one location of names and reputation, rather than 4 separate ones. I am a programmer, but dabble in IT stuff at work(so just for work I use stackoveflow and serverfault). When I am home I am also a hobbyist and use superuser and now I am writing you and needed a 4th account.
I just feel one rating's system with a uniform user-base will add to consistency and ease of use for your users.