For me this is a hard one.
I agree with everyone.
I have mixed feelings about dog parks.

I think if everybody's dog is friendly,
poop is picked up right away, shots up to date,
it's a great way to socialize your dog and meet people too.
I think it is important not to have any aggressive
dogs at the park "period".

When dogs play, and the play gets rough, make
sure that all the dogs are having fun.
Dogs tend to pack up, and pick on a weaker dog.
Sometimes fun play turns into a argument seconds later.

I think the lady has some screws loose.
Her dog is going to seriously hurt another dog, or
somebody elses dog will seriously hurt hers.
Her dog should "NOT" be at the park.

Don't you enter dog parks at your own risk?
I think a registration is a great idea.