The basic idea sounds reasonable enough. Why not have the government nudge citizens along the path to righteousness by making bad choices more expensive? But even the most avid proponents of sin taxes concede that none of the nickel-and-dime proposals on the table is large enough to discourage soda drinking. And they're not really intended to. Soda taxes, like most sin taxes, aren't primarily designed to reduce consumption.
It's a must-read.