Instagram is a free photo-sharing social network designed to share images across a mobile cellular network. The company was founded by Kevin Systrom and Mike Kriegerm, two fresh-faced Stanford graduates. It was their second venture. In April of 2012 Facebook paid a billion dollars for the company; currently the deal is pending FTC approval before all is said and done. Pretty good for a business that has not even begun to turn a profit yet.
An instagram image is different from the 4:3 format of most mobile camera devices in that the picture produced is in a square, similar to an old Polaroid or Instamatic photos of yesteryear. The images may also be tweaked various ways (shading, splitting, change-of-focus, etc) to make them look different and in turn make the photograher feel less like a lame douche and maybe even identify as arts-y.
Instagram allows its users to make their own unique hash tags for their photos. Unregistered users may view instagram images the same way that one may view tweets.
Within its first two months of operation, Instagram already had one million users. When the Facebook aquisition was announced this past April, there were over 30 million users. Given the proliferation of smart phones and humanity's common love of documenting moments on the fly, it is no wonder that instagram has become a modern household name in just two years. Needless to say, people love it.
Recently an instagram aggregator has appeared, that displays all the instagrams uploaded just now in major cities, as well as across the globe. Note that all instagrams are public to non-users unless an account is specifically set as being private.
Also, there's a small collaborative project whereby different electronic musicians composed works to accompany different instagrams. It's called Instagr/am/bient.
A portable device with a larger display is being developed to sync instagram account: instacube.
And because rich + youth = [ridiculous shite]: there's now a tumblr devoted to rich kids of instagram
& another inevitablity: Mexican pop band The Plastics Revolution made the first music video which is composed entirely of Instagrams.
On December 18, 2012, it was announced that Instagram will be changing their Terms of Service—specifically their policy on privacy, effective in the new year. These changes include a long string of legalese stating effectively that Instagram they now may license users' content for any and all advertising purposes. Many users were shocked and vociferously complained. Faced with the prospects of losing their their userbase, the company reverted back to their original TOS within the week.
Addendum: while at least one imitation service has begun, it seems that most Instagram users have still use the service somewhat, if not as often as they did initially.
And in Kuwait, people have begun using the service as a marketplace in which to sell eveything from manga to sheep. This practice is so popular that there is now an expo devoted to the entreprenurial use of Instagram.