I've only heard of two Mistresses with basically the same name in the same city once. It was in NYC years ago and I sessioned with both. One used a first and last name, I'll call her "Mistress Mary Jones." She was mature and in the scene for around a decade. The other was a younger, up-and-coming dominatrix, I'll call her "Mistress Mary." Both advertised in the local BDSM tabloids and early internet sites, and both showed their faces in their print and web ads. Aside from their age differences "Jones" was a tall blonde, the younger domina was a shorter and athletic brunette, and they offered slightly different activities. There was no way a sub would confuse the two, but "Mary Jones" spoke to "Mary" about it. The younger dominatrix changed her name, trying to avoid a hassle. "Mistress Mary," who mentioned the story to me after that said her business was not hurt by the change.