One downside to non-braced conditionals is that a semicolon accidentally placed after the conditional will cause the block to always run, e.g.:

  if (null != foo);
    bar();

This is valid code in C and Java, and bar() will always run in this case.

Having seen people waste hours on such a semicolon, I always use braces, even in one-liners, because I never know when someone is going to break it out into multiple lines later:

  if (null != foo) { bar(); }