I saw the series of pictures of the Mexican pyramid light and think it might be a hoax, in that the photographer took a pic of his daughters and, as they were purportedly presented in order, one of the pics had the light but another did not, and it looked like the exact same photograph of his daughters, perhaps seconds apart. If the light was "for real", it was instantaneous. The one of the Bosnia pyramid was a video, and I couldn't tell if it was fake or real. My understanding is that the pyramids are not "open" at the top, they are platforms.
Along this same line is the guy who believes the Great Pyramid was a "fueling station" for UFOs. From the Chinese there is a story about aliens who came to China and enslaved them, forcing them to build the Chinese pyramids, and fueling their spaceships from atop the pyramids (also flat-topped). According to Chinese lore, they were finally "saved" when red-haired giants fought off the aliens. Finally, we have the story from the Russian taiga where the natives report pod- or bullet-shaped objects coming from under the ground and firing something akin to light beams into the sky, perhaps to destroy an incoming asteroid or UFO. I don't remember the provenance of each of them, but the stories are searchable on youtube.
I have no theories, but I'd like to know of any, too. Lots of food for thought out there!