The bipartisan tax reform bill recently introduced by Sens. Ron Wyden, D-Ore., and Judd Gregg, R-N.H., proposes to abolish IRC section 911. That section, which exempts U.S. citizens living overseas from tax on the first $80,000 of earned income, is indeed anomalous in the context of a tax on all income "from whatever source derived," and has been subjected to criticism. However, there is a reason section 911 has been in the code since the 1920s: In its absence, citizenship-based taxation becomes completely unadministrable. Rather than continuing the long argument over section 911, Congress should therefore reexamine the basic premise: Should the U.S. continue to tax its citizens who live permanently overseas?
Avi-Yonah, Reuven S. "The Case Against Taxing Citizens." Tax Notes Int'l 58, no. 5 (2010): 389-94.