Comment by msm_

But of course there is. Imagine the following compression scheme:

    0-253: output the input byte
    254 followed by 0: output 254
    254 followed by 1: output 255
    255: output 10GB of zeroes

Of course this is an artificial example, but theoretically it's perfectly sound. In fact, I think you could get there with static huffman trees supported by some formats, including gzip.