Ed Hardy and another tattooist make reference to this subject near the end of tattoo the world. If I remember correctly it's shrugged off fairly casually as flattery and something a successful artist can expect.
A pretty mature response(IMO) that they spend very little time on. Sorry I don't recall the other artist but it's at about 15-16 mins left when it's brought up.
Of course in a perfect world, such things would not exist and everyone would 'play by the rules'
But similarly to the thread where dude tattoos 'DRAKE' across that young lady's head, the FACT is, that if you don't tattoo it, someone else will. Unlike a couple decades ago, the market is full of tattooers of varying skill level, unlike before if a good artist turns you down now, there's another good artist who will take your money and make you a good tattoo.
I'm in no way advocating that tattooers should tattoo whatever comes comes through the door, I merely stating the obvious fact that for every customer willing to bend the ethics there's an artist willing to participate. The willingness to participate is is a choice the customer and tattooist have to make. I feel like, just like any other industry, ppl are going to do what they feel is 'right' but ppl are also going to do what they have to do to eat and pay the bills.
Similar situations or parallels can be drawn in any industry. Make your personal choice as a collector and artist(in our context) and stick to it.
Personally I'm pretty indifferent as to what other ppl get tattooed on their bodies and unless someone is passing your work off as their own, I lean towards looking at it as flattery, but of course I haven't been active artistically in over 15 years, I suppose It's possible I'd feel differently if I made my living making art(if any form).