This isn't much of an issue for the Celebrity, but Demagogue bards will have this issue. Incite Violence is one of their main draws, so the inability to effect many people in their crowd seems a bit weak. Take a level 20 Bard demagogue for example. They can fascinate all of 7 people. The number of people they can gather will easily be around 400 though. Probably even more.
The ability mentions that you can fascinate the crowd to keep their attention, but it really does seem that something is missing. The amount of people you can fascinate is pitifully low for being the main focus of both the Celebrity and Demagogue.