2020 UPDATE From the Xbox One version of the game and Facial La Fleur guide:
It's been recently discovered that this achievement is obtainable once again by utilizing a simple workaround to trick the game into believing you've successfully contacted the now closed Ubisoft servers.
There is no need to remove friends or block followers, as stated by the other solutions. Once you've played a short time, and have acquired some Oculi through looting a few chests, you're ready to begin. Follow the steps below exactly and you shouldn't have any problems unlocking this achievement.
1. Press the button and select Oculi from the options.
2. Choose any of the three equipment slots to see your available Oculi.
3. Highlight the Oculi you wish to give away and press to Gift it.
4. Choose a friend to send the chosen Oculi to and press to Confirm.
5. Be ready to pull your network cable from the back of your console and press to Confirm once again.
6. Immediately upon seeing the "Sending Gift..." dialogue box, pull the network cable and wait until the process completes.
7. On the next confirmation box, press once more to acknowledge your Oculi was sent.
8. Plug your network cable back in to your console and the achievement will unlock.
Per jGuiiLe this can be done with a wireless connection as well. In step 6, power off your router when "Sending Gift..." displays and power it back on in step 8.
If anything seems unclear, please comment and I will try to elaborate. Good luck.
Note: If you're starting a new game and don't want to hunt down any chests, you can purchase some Oculi from the uPlay app if you have any points to spare. You get 3 for 10 points, so you'll have 3 effortless attempts at this achievement.
Shortly after the start of the game you will exit a cave by pushing a box against a wall. after jumping on the box go up the path to you left. Across the chasm you will see chest that you can use your firefly to open. inside are two Oculi pieces. Select one in the menu and push X to send it to a friend. Easy 10G
(Edit) Make sure you have a Uplay account before going of this.If by chance you don't, go to the Uplay website, once you have an account you can add and remove friends directly from the app
(edit 2) Seems like more people are having luck when they seriously trim down their friends lists.
(edit 3) it looks like the achievement has been patched and there is now no need to delete friends thanks to ChaosSlayerX187 for sending this info out