From what i can see, it does not seem to work. Here in western Europe in the big cities many people buy locked phones second hand and the vendor explicitly says you have to get it unlocked, which is a service provided by many phone shops (somewhat under the table).
These locked iPhones sold for 50-200€ are acquired by users who will turn to their tech friends/neighbors to get it unlocked. When these tell them they can't help with that (no package in Debian for that yet), they end up spending 20-50€ in a shop to get it unlocked anyway, financing a very shady market.
Previous discussion on HN: https://news.ycombinator.com/item?id=19845934
Quote from the article that sparked the discussion:
> To do this, they phish the phone’s original owners, or scam employees at Apple Stores, which have the ability to override iCloud locks. Thieves, coders, and hackers participate in an underground industry designed to remove a user’s iCloud account from a phone so that they can then be resold.
At the end of the day, if the thief doesn't get the phone unlocked themselves, they will sell the phone for half (or less) the price they would have sold it unlocked, but they're still making a buck.