Small hands... I'm similarly afflicted by this dilemma, although what I've found over time is that small hands are not so much as an insurmountable problem. Granted, at tims they may present difficulties to the player or performer - but nothing that cannot be ameliorated.
My right hand, since you asked for spans, can reach an octave - nothing more. My left hand can reach an octave - nothing more.
I'm in 10th Grade at school, however, and have the third-smallest hands in my entire grade. So yeah, my hands really are small - let alone for a pianists'.
However, even with these apparent handicaps, I've played pieces such as the Chopin Etude Op.10 no.1, the Liszt Orage, the Balakirev Islamey, the Chopin A flat Polonaise - as a rule of thumb (...), I've found that as long as you can reach an octave, then one should be fine as far as repertoire and physiological capability is concerned.
There are ways of helping the hand overcome its lack of physical size - as other posters previously said, there are exercises and other such actions one can take to stretch the fingers, as an athlete or sports player stretches his or her limbs. Also, pieces designed to open up the hand, such as the aforementioned Chopin Etude, can help in terms of technically dealing with the shortcomings of a smaller hand.
All in all, it's not really an impossibility to play big repertoire with small hands. It is true that those with bigger hands have an advantage, and relative to them, that puts us at a disadvantage - but it is nothing that cannot be overcome.