I personally think it’s tacky. My husband and I thought it was tacky twenty years ago when we got married. Out of 7 weddings we attended the year we got married–not counting our own–only one did not include this “tradition” and of the other six, only one did the bride laugh. In three, the bride retaliated angrily (one grabbed the top tier of the cake–normally reserved for the first anniversary–and let the groom have it. Turned out they didn’t need it anyway.

) In the other two, she burst into tears.
Over the years, I’ve seen more of an acceptance of this “tradition”. In the few where the couple decided to forego this “tradition”, I’ve heard guests express disappointment that the couple didn’t do it. Two instances in the last year or two stand out. Both times, I made the wedding cake for the couple. In the first, the bride confided to me that she and the groom had discussed this in advance and, with the wedding cake being all chocolate and covered in strawberries, they had agreed to NOT do the cake smashing “ritual”. They cut the cake, placed it on a small plate, then the groom fed his bride a small piece of cake on a fork, then she fed him a chocolate-covered strawberry. It was very sweet. But then I couldn’t believe what happened next: They were actually BOOED by the guests!
The second time, a very young couple (he was 20, she was 18) came up to me and said they wanted ME to cut their cake for them, so as to avoid being asked to do the cake smashing. I said it would be nice for them to cut the cake together, just for the photos. They agreed to do that, but the groom said, “But we don’t want to feed each other cake. We don’t want our guests to start asking us to have a food fight!” I said, “Honey, it’s YOUR wedding. You do what YOU want to do!” So they cut the cake, had their pictures done, then they handed me the knife and server and bowed out while I cut the rest of it and served it. Three photo hounds (all family members) followed me to the couple’s table when I served them their pieces and waited for the cake smashing. They were quite affronted that it didn’t happen.
I guess that’s what bothers me the most. The fact that a lot of guests EXPECT this behavior nowadays. That they’re actually disappointed when the couple doesn’t smash the cake in each other’s faces. To me, it’s a sad commentary on society–to get entertainment from other people’s embarrassment (oh, believe me, more people get a kick out of seeing this ritual when the bride ISN’T expecting it so they can see her fight back!)
But if anyone wants to do it, hey, like I said, it’s YOUR wedding, do what YOU want, but don’t expect me to think it’s cute or funny.