When you're a game company and you're trying to tease some new content using augmented reality games to help bring the whole thing to life, you better make sure you plan it out right, otherwise the internet will solve it much faster than you think.
That's exactly what happened with Overwatch's ARG for the new character Sombra, as explained by Kotaku. Lead hero designer Geoff Goodman explained to them that they had never done an ARG before and setting up real life puzzles and clues for people to follow to uncover the content. Thus, they ended up having to stretch the ARG for Sombra because originally the puzzles were supposed to take gamers so long to figure out that they wouldn't uncover all of the details until BlizzCon, but things didn't work out that way.
In fact, once the ARG started in July gamers had already pieced together that the new character was Sombra thanks to some leaks and a lot of social media coordination. According to Goodman...
Blizzard was unsure of how difficult they needed to make the ARG in order to keep gamers both interested and active. They also weren't sure how difficult they needed to make it in order to prolong the ARG for Overwatch so that Sombra was properly unveiled at the right time (which was supposed to be BlizzCon).
Most of these ARGs are solved rather quickly in the gaming community because the entire culture is built around progressive problem solving. Games are little more than conceptual challenges set within virtual demarcations for the brain to solve. When you have a puzzle or challenge that goes by certain rules, gamers are awfully quick to adapt to the situation and begin to solve the puzzle(s) based on the rules of the challenge.
The only company who managed to royally stump gamers was Valve with their ARG during the Winter Steam Sale last year that had gamers scrambling to uncover all the clues within the span of just over a week. There were a number of things alluding to what people thought was Half-Life 3, but even then it turned out that gamers had taken a dive deeper into the ARG mechanics than what Valve had originally intended.
As for Blizzard, the article notes that while the Sombra ARG may not have turned out the way they wanted, it did give gamers something different to look forward to with unveiling the new character for Overwatch.
They don't have any new ARGs planned for the near future of the game but it's not off the table completely. Goodman mentions that they don't want to wear out the ARG concept on every new character they introduce into Overwatch and that they would prefer to focus on introducing each character based on a theme that best suits their personality. In this particular case, a character centered around hacking seemed like a perfect fit for an ARG introduction.
Sombra, meanwhile, heads into the Public Test Realm for gamers to offer feedback on, and will soon join the cast of playable characters in the first-person shooter very soon.