As a JW, I was called to jury duty but I kept careful documentation so they couldn't call me again until the two years were up. My understanding, at least for my experiences here in the U.S., is that they get you shortly after you visit the Department of Motor Vehicles; whether you're registered to vote or not has little or nothing to do with it. So...probably I'll be summoned to jury duty again next year after I renew my registration on my car.
I never had to even see the inside of a courtroom while I was a JW, but last year I was put on a 4-day trial, but after it was over, I was told that I was an alternate juror and would not partake in the final decision. To be honest, it would be nice to have the JW status so I could refuse it, but not so nice if they decided to put me in jail for it or something. Besides, I guess people have to be involved in the process if it is to work even to the extent that it does, so...I get it.
--sd-7