I guess there are unwritten rules in the industry, and for me, to many of them are about "respect". Lots of artists who have been working in the industry for 20 + years are covered in tattoos, but I would not let them near me with a needle, even though they are well respected. Some of the newcomers who put out amazing work have little tattoos, but receive little respect from the industry because of how long they have been around. The average customer does not hang around forums like this, they come in off the street looking for something "nice" from the flash. I do not think they care how long the artist has been around, how tattooed they are, who sponsored them etc. For them its about the "experience" .My wife is about to start her apprenticeship, and has only 1 tattoo. She wants more, but is cautious by nature, so when she knows what she wants, and who by, she will undoubtedly get more. But the artist she will be working under was happy that she had only 1 tattoo, so that she knew what it felt like. He was more interested in her artistic ability, which again, is what the average Joe is concerned about.
So for me the answer is that I care more about the tattoo they are putting on me than the tattoos they have.