On the other hand, it's actually just the , also known as (which refers to "power" but alternatively to "standby" or both "power/standby") as well as , where it refers explicitly to the "power control user interface." It's also on Apple laptops, Windows-based laptops, desktops, various other electronic devices, and if you look at the touch button on your PS3 -- yep, it's there too. That it's green may have some significance...or it may be a red herring. Hard to say.
Some are speculating the lower case 'i' is for iPod, and that the exclamation point has to do with the logo for .
What else do we know? Not much. We know the word "Solid" isn't in the teaser, so that lends credibility to the Metal Gear Acid theory. There's also Metal Gear Online to think about, and possibly Metal Gear Mobile. Perhaps a Metal Gear for the iPhone?
On the other hand, the URL for the teaser () contains the letters 'mgst'. "Metal Gear Solid Tactics" for [insert your theory of choice here] anyone?