The Xbox racing game touts artificial intelligence powered by other players and your friends as the future of online gaming. It’s hard to find a time when you and all your friends are available to play the same game at the same time. Everyone lives hectic lifestyles with schedules that never allow for a large chunk of time for gaming. The Forza series of racing games have solved this problem by cloning your friends onto their servers.
“We suggest you think of your Drivatar as a clone of yourself. It is a replicant […] a realistic model of your own driving skills.” 
The Forza series of racing games are some of the best racing games available. They focus on enjoying the scenery and the driving experience over realism and simulation. Except when it comes to the opposing drivers.
Drivatars are great!
The drivers will be your Xbox LIVE friends, or rather: a virtual representation of them. It’s more fun to beat people you actually know than to to beat random strangers or computer simulations. As an added benefit, your opponents are much more unpredictable and feel more alive than in other racing games.
“It’s not online play, and it’s not a straight recording of you driving a particular track — it’s something much more complex and interesting.” 
As you play the game, a shadow copy of your driving style and decision making is used to create an online artificial intelligence powered driving avatar or “Drivatar”. The Drivatar is constantly updated to reflect how your skills in the game improve or worsen over time. Your Drivatar then appear in strangers’ and your friends’ games to race against them. Preserving the concept that it is more fun to play against your friends without actually involving them when you play.
What Turn 10 and Microsoft — the developer and publisher behind the franchise — achieve with the Drivatar system is the feeling that you are actually playing with an interactive version of your friends. When I am driving around in the open‐world roaming Forza Horizon series, I see other drivers passing me by in every direction. The world is filled with other players.
I can suddenly see a name I recognize pass in the opposite direction while playing. I throw my car around and I race after them, press the X button to initiate a head‐to‐head race, and start racing against them then and there. Adrenaline quickly kicks in and I’m thinking “I have to beat my friend in this race!”
There is even a micro‐transaction and social‐pressure mechanism involved. Your Drivatar earns you in‐game currency for every race it appears in. As your Drivatar is much more likely to appear in your friends’ races than strangers’, you are incentively to encourage your friends to regularly play the game.
No shared experiences
With Drivatars, your desire for competitive engagements against your friends are fulfilled. The only trouble is that you have not actually raced against your friend. Your friend and you have no shared experiences from the event. Your friend is not even aware that you just beat him on the track by an impressive 2 seconds and 372 milliseconds! The next time I talk to that friend, I find myself bragging about how much better I drove and how he totally lost his lead by messing up that last turn (as his Drivatar often does).
I have found myself complaining to one friend about the behavior of his Drivatar. He/it drove so dirty and sabotaged so many of my turns by ramming into me that I had to temporarily remove him from my friends list. He, of course, had no idea what I was talking about at the time. The same friend, some time later, bragged to me that he was now beating my Drivatar in every race. Which, of course, I knew nothing about.
I believe this weird hybrid online interactions with friends can become a social problem over time. Right now, these kinds of interactions are limited to some games and maybe some odd advertisements online where your friends unwittingly endorses products they have bought previously.
Microsoft talks about Drivatars as clones in their marketing material for the technology. The idea of your personal relationships being thinned out by weak online interactions with a pale ghost of your friends just does not sit right with me.
I’m not sure what Microsoft can do to make the situation better. However, I sincerely hope they will find some way — other than Xbox’s built‐in game DVR feature — to make the game moments that matters a shared experience with your friends. I’m not sure if automatically sending them video clips and status updates is the right way to go about it. It’s a human–to–human interaction problem, and I’m not sure software can solve those.
-   Drivatar Technology in Forza Motorsport at Microsoft Research
-  Forza Horizon 2: What’s a Drivatar, and why should I care? in Xbox Wire