Reply #10: the cable spooler is the first counterweight.

[phantom power]

There's a pretty good faq at this link, which includes a fairly detailed explaination of how they plan to deploy it. The satellite that spools out the CNT composite ribbon is the initial counterweight. Once you have the first ribbon deployed, it is then cheap and easy to ship additional counterweight up, as needed.

Also, the cable itself extends *past* the geosync orbit, by quite a bit. So the cable itself provides some of the counterweight.
http://www.liftport.com/faq.php