Usually while configuring Salesforce, you'll be logged in with a User that has been assigned the "System Administrator" Standard User Profile. When you're using this type of account, you typically think you have access to and will see every configurable part of Salesforce.com that your Org has.
This isn't always the case - take for example the "CTI 2.0 or Higher Settings" section under Setup --> Customize --> Call Center --> SoftPhone Layouts --> Edit --> Inbound Calls.
This is what I was seeing:
This is what I was missing:
According to the documentation, "This section only displays if your CTI adapter was built using the CTI Developer's Toolkit 2.0 or higher." While working in a client's Org, a 2.0+ CTI adapter was being utilized in both their sandbox and production Orgs. Within their sandbox, I was able to see this section, whereas in production, the setting was missing.
Naturally, I wondered if it had to do with release differences, but the sandbox was Spring '14 and production Winter '14.
Setup-wise, they were identical with one small difference - my user account was no longer listed as a User under the Call Center's settings (Setup --> Customize --> Call Center --> Call Centers --> Click on the Name --> Click on the "Manage Call Center Users" button).
Once it was added back, voilà! The "CTI 2.0 or Higher Settings" section was back.