I haven't had experience of this, but have often seen comments on the thorntree.lonelyplanet.com forum that the craigslist sub-let may sometimes not be permitted by the terms of the lease so it could get messy.
If a ticket requires 30,000 points and my partner and I have that much between us (but not each) is there a way we can give points to the other, or pool the points to get the ticket?