While not a very useful application, Food Fight does demonstrate the intrinsic power of playful social interaction over glitzy effects.  Food Fight, developed by David Gentzel of Virginia Tech (Go Hokies!), extends the psychology behind the poke.  As in MMORPGs like Warcraft or with virtual roses in Hotornot, users of the application spend a virtual currency on a menu of food items to toss at their friends.  The items show up on the FF widget on the target profile.  A whole list of tossings shows up on each person's FF application page.  The major glitch in the idea is that the recipients must have the application installed to receive food thrown at them.  But you can invite friends to install the app and judging from the discussions on the app board, the grade school audience seem to be big fans of it.  Food Fight has 200,000 or so users today.  Each user is alloted $5 to spend on food per day and the virtual credit is free.