Out of Control Baby and Parents Do Nothing.

So, if I was in your position, I would hide in the closet when I saw them pull up in the driveway!

I had the same problem with my nephews. My sister and her husband do not believe in the word no. They also do not believe in sticking with any threats they may say to the kids... you know, like "if you do that again, we're leaving." If anyone needs Nanny 911 it is my sister!! And it sounds like your friends do too! (My sisters kids are now 8 and 5 and are still the worst behaved kids I have ever met!!)

They need to get a grip on this child ASAP before it is too late... too late to change his behavior, but even moreso, too late before he really hurts himself.

I would give them an ultimatum... either they stick to your rules in your house, or they can no longer come over. It might ruin your friendship, but it could also save your house and your peace of mind.

L. I think it's time for you to talk to your "friends" and tell them like it is. If your friends can't respect you and your house are they worth having? Don't let people walk all over you and your stuff. Let them know they need to call you before they visit. It sounds like they don't respect you and your belongings. You need to be honest with them.
You have every right to say no to the baby when he/she is doing something wrong. This is your house and every house has rules. I really hope you can tell your friend your feelings and even suggest visiting them at their house instead of yours. That way you have control over when you see them.
If you don't put down your foot now, things are just going to get worse. If you give a person a foot - they will take a mile.
Be strong

My assumption is that these people are either family, neighbors or people that you "have to deal with" on a regular basis.

I think besides the obvious things that other people have said about setting ground rules..... I think that can be rather difficult given certain circumstances.

I would suggest limiting their time at your house. Make excuses why you/they have to leave.... you have a doctor appt, you need to get your oil changed and this time you made an appt for it.... whatever you have to say to minimize their time in your home.

Not everyone should have to baby proof their homes, but if these people are over on a regular basis and you like their company (minus the little boy) then you should make some effort to baby proof some things. Keep expensive items up on a high shelf, things you dont want him to touch - place temporarily in another room with the door shut. It is an inconvenience to do this but then again it is ultimately your choice to let these people into your home, sometimes you have to make sacrifices.

ok who are these people and do you provide childcare for them or are they friends? what is the background?

And these people and their baby are FRIENDS? You need to set down some rules in YOUR home. Tell them they are not allowed to just "drop in" anytime they feel like it. A phone call to ask if you're busy and open to a visit is necessary. Tell them that although you value their friendship, it's upsetting to have their child wreck your home and it makes you very angry that they do nothing to stop the "little dear."
Also tell them that if their child breaks anything, you expect them to pay for it. If there are messes left behind, you expect THEM to either clean it or pay to have it cleaned.
Maybe with a few rules as above, they'll not visit quite so often.