Anonymous hubs serve as the intermediary between you and the Internet.
When you wish to access something on the Internet, your request is
sent to the anonymous hub, which then forwards it (anonymously) to
the intended destination. When you're using a proxy, you already
have an intermediary between you and the Internet. If GhostSurf
sends a request which has the anonymous hub as the ultimate destination
to your proxy, the request will reach the anonymous hub--but the hub
won't know where to send the request.
Effectively, your proxy serves as your anonymous hub. When it sends
out your requests, its IP address is used in place of your own. It thereby
supercedes the functionality of anonymous hubs. You can verify this by
using GhostSurf's "Test Connection" feature; the backtrace from
privacy.net will point to your proxy, but not your own computer.
However, your proxy (like anonymous hubs) does not remove personal
information from the requests you send. GhostSurf still provides this
and all its other privacy-protection services for you.