Also, c'mon. Glibness is a spell whose value ranges from "useful" to "overpowering" based on how the GM runs social stuff, but it's not going to make-or-break the Bard. I mean, hell, you've got Charm Monster and Lesser Geas at the same spell level; you got Suggestion one spell level earlier (and one level earlier via your music, potentially), and Dominate Person one level later. Not to mention a high Charisma, Diplomacy, and all the synergies. You've got lots of options for social command-and-control-- and even that is just one trick in your bag.