It works absolutely fine if you don't skid. If you skid you can unscrew the cog. Rotafixing the cog on TIGHT will minimise the possibility of this. Always a good idea to run a front brake regardless, doubly so with this setup. I would have no problem with it as long as you have a brake (both my fixed bikes are set up this way and I tend to skid with hands on the brake hoods.) If you do unscrew the cog you just lose your breaking, it is not otherwise catastrophic. As you should not be skidding for emergency stops you will generally then have time to use your front brake instead when this happens.
It works absolutely fine if you don't skid. If you skid you can unscrew the cog. Rotafixing the cog on TIGHT will minimise the possibility of this. Always a good idea to run a front brake regardless, doubly so with this setup. I would have no problem with it as long as you have a brake (both my fixed bikes are set up this way and I tend to skid with hands on the brake hoods.) If you do unscrew the cog you just lose your breaking, it is not otherwise catastrophic. As you should not be skidding for emergency stops you will generally then have time to use your front brake instead when this happens.