Originally Posted by genericbikedude
You really don't need rear brakes at all. In my experience, they hardly do anything unless you have discs or very good vbrakes. If you don't like your fixie in congested areas, consider lowering your gear ratio.
my old bmx only ever had a rear brake (against regulations to have a front brake when racing), and I could always stop just fine. it's not so much the brake, but the set up. do a crappy job adjusting the brake, you'll get crappy performance.