Pretty much any amount of tattoos are an acceaptable amount for me as long as it's good looking tattoos.
Though some people are grossed out by there being a single tattoo on a girls arm or if they can see the outline of her abs, guess they cant stand her being in better shape than themself.
I'm talking about those people with 100% of their body covered in tattoos. Too many tattoos look really ugly, especially if they don't fit together well as a whole. IMO the best ones are the whole arm tattoos, given they are done properly and with style.