Trish, a lot of the dancers specialize in a few dances and become very expert at it but still participate in all the dances. Do you know it can take up to a year for a woman to make and decorate her dance regalia (dress, moccasins, etc.) and the dress can have as much as 20 pounds or more of beads on it?
Yes, some people do feel that PowWows are exploitative to Native Americans. However, what most people do not understand is that the PowWows are not put on for the benefit of non Native Americans - they are not performances for the general public. Even though most of them are open to the public, these PowWows are ceremonies that are spiritual in nature and each one is for a specific purpose, to commerate some event, holiday or person. A lot of these ceremonies are closed to the public because of the secretiveness of the sacred ceremonies and rituals.
Generally accepted rules at PowWows are to not applaud, do not point, do not take photos, do not approach the dance area, do not dance unless invited by a tribal leader and never join a drum circle unless invited by a tribal member of the drum circle. There are other common sense rules, but the purpose of pointing these out is to show that the Native Americans involved in the PowWow are not "performing" for us - they are conducting ceremonies for their own reasons.