Dealing With Dangerous Dogs

Here's a question, what do you do when your neighbor has a dangerous dog?  Now this is BASED on a true situation and the people have been very cool about it.  I'm almost 100% positive that they're going to fix the situation and everybody will be happy, It just got me to wondering.

So my friend has a puppy. It's never even been close to an aggressive dog.  Even though he's a bit of a bruiser, he's never met a mean dog face to face.  The next door neighbor has a very aggressive dog that goes nuts whenever somebody is in my friends backyard (literally foaming at the mouth nuts).  He also has shown signs of trying to dig through into my friends yard.  Let me also mention that it's her fence.  She had it built before there were any neighbors to help share the load.

I wrote a nice note to the neighbors telling them I had to block off her side of the fence with cinder-blocks and would they please do the same for their side. I let them know that nobody is mad and dogs will be dogs.  I'm pretty confident they'll do the right thing. They've been pretty cool people so far.

This situation isn't that out of the ordinary though.  My question is, "how have you dealt with aggressive neighbor dogs?".  Seriously, I don't think you should be afraid to take the trash out through your own backyard or fear for the life of your animals.  Do you think asking nicely will be or should be enough?  I will also tell you that one of my own dogs had to be put down for attacking other dogs (sadly, he showed no aggression at all towards people).

What do you guys think?