Reason #1: We have no idea what song he's going to perform, so we're definitely going to be surprised when he starts singing.
We're fairly confident when we say that Justin Timberlake is going to perform "Suit & Tie." But, we're really not sure what route Frank Ocean will you. If he plays it safe, he'll go with "Thinkin Bout You." But, Frank doesn't seem like a "play it safe" kind of guy, so we could literally hear anything when he takes the stage.