Face tattoos blur because the blood circulation to your head is much better than othe places on your body. That's why even small head wounds bleed like crazy. The extra blood flow make the ink spread too much. It's much like getting a tattoo when you're drunk (because the alcohol thins the blood and that also makes the ink spread). I'f you've ever seen those 'gangsta' teardrop tattoos, they last about 3 months or so (if they are done really well) before they start to blur out.
I don't think that's always the case. My dad has a friend that's in her 40's, she's got a little teardrop tat by her eye, and it's been there for as long as I've known her. And as far as tatooing the face goes, what about that crazy shit some people do, like tatooing make up on their face? I saw something about that once, where women get eyeliner or eyebrows or lipliner tatooed on them.....maybe it just depends what part of your face you get the tat on.
A close friend of mine runs a tattoo parlor (that's where I got mine - the design is also my avatar). I'm only going by what I was told. We've talked about it quite a bit, but She isn't a tat artist, she just rents them workspace, so perhaps she isn't as knowledgeable as I had thought.