If I intentionally block SDUpdate.exe from accessing the internet, I no longer get a "Socket Error # xxxxx" message as updates using SpybotSD.exe would issue in the past. Instead the update process just issues a "No newer updates available" message after a 30 second delay.
In addition the Update downloads.log appears to indicate that the spybotsd.ini file was actually downloaded even if no internet connection was ever established. The only way to determine that the spybotsd.ini file was never downloaded is that the online.ini is empty after the update attempt.
By issuing a "No newer updates available" message rather than an indication of a failure to download the spybotsd.ini file, users can be mislead and may not realize that there is a problem such as SDUpdate.exe not having access to the internet through their firewall.