I dont think it was planned. At events like this folks are always having cameras on the big stars, especially ones that were nominated and are possibly about to win. Thats why a camera was on Beyonce.
And I dont buy the publicity line either. Making Taylor Swift cry on stage is probably #2 on a list of things to get you to look like a bully, right behind stealing the youngest Jonas brother's lunch money. Theres bad publicity, and then theres BAD publicity.