Prediction: 2010 will be the year of game mechanics
I kind of dread this, actually. As with the “now 150% more social!” and “it’s podcast-ic!” trends of yore, hundreds of craptacular “look! It’s a GAME now!” bolt-ons are being designed by committee as I type this.
Adding a “foursquare”-like game to your web service is going to be the hot new thing.
It’s already started with Glue; see Fred Wilson’s post.
