Actually it appears we were both mistaken. There is no long-term annual tax requirement for former US citizens, though if you retain your citizenship you do have to keep filing US taxes regardless of where your income comes from.
http://renunciationguide.com/Residents-Non-Resident-Citizens... and
http://renunciationguide.com/Exit-Tax-on-Renunciants.html provide the relevant details. In short, things changed significantly in 2008.