Recently, it was officially revealed during the Spike VGAs that Mass Effect 3 was to be released during Holiday 2011. Even though EA goofed and accidentally revealed their hand, there were still gamers who figured out this unveiling well-before today's award show due to the numerous hints and clues that Bioware put out.
It all started with this Bioware teaser video that was uploaded on November 17th which included a split-second look at this:It wouldn't take long before hardcore Bioware geeks pegged the weapon that the soldier was holding as the Incisor Rifle from Mass Effect 2. From there, the speculation went back and forth to this being a spin-off multiplayer title set in the futuristic world to a possible full-fledged sequel.
Enter the second set of clues:Several QR codes were updated to Bioware's official Facebook and Twitter pages which would reveal the following to anxious gamers:
1st Code - Converts to 55.845 (atomic weight of iron atom)
2nd Code - Converts to -128.5°F (unsure of what this means)
3rd Code - Converts to the url of the UK Secret Intelligence Service
4th Code - Converts to a url of the album cover for The Clash The Singles
These clues lead to believe that this unknown Mass Effect game was going to be set on Earth and would take place in the UK, due to the last two codes. The 2nd code could either be one of two possible things: a location in Antarctica or a reference to a planet from Mass Effect, Aequitas.
One NeoGAF poster, Nirolak, even managed to conclude exactly where that soldier in the original teaser video was actually firing from. Vauxhall Bridge, near the SIS headquarters (3rd code), can be found on both a satellite view of the area and the image below:Click here for NeoGAF thread that managed to decode and compile all of the above info. You can read about the clues in more-detail or view a month's worth of posts with people arguing/deciphering every hint. I particularly love the one-two punch of post #2 and #3: Love it.