Text messaging in a huge pet peeve of mine. Not the actual text messaging itself, but the way a lot of people do it.
Texting while someone is talking to you, text messaging during a movie at a theater (Man, that light glows!). I've even gone to a store check out and felt as though I was interrupting the cashier because they were too busy texting to do THEIR JOB!
But this? This takes the cake! Wedding Cake that is.