Originally Posted by john_and_off
Thanks for the input, everyone! More or less, from everything people have said here, I've come to the conclusion that given my riding style (like I said, I ride pretty conservatively) and the fact that Boston is pretty flat, I should be fine with just a front brake.
There is one other issue that noone seems to have brought up. If you ride in crappy weather on crappy surfaces a rear brake will greatly improve saftey. There are situations where you not be able to stop as fast as possible with your front wheel as doing so would cause your it to slide and you to go down. In such circumstances back pressure on the pedals is a really crappy way to stop since it can not be applied evenly and will cause the wheel to slide and make you more likely to go down.
if you ride on surfaces like these regularly you might want to consider dual brakes even on a fixie
-wet brick
-ice
-wet leave covered crap
-sandy roads