The better thing to do is have a contract, and if the client doesn't pay, have a lawyer send a threatening letter warning them about contract violations and court action. That should work almost every time, and if it doesn't you'll already have a lawyer familiar with the situation.
For bonus points, have the contract gone over by a lawyer before signing it in the first place. There are law practices and legal services businesses that specialize in it and it only costs a few hundred dollars. And it can be added to the cost of the project.
For number 1: A contract review can be done for around $200. Other than bottom of the barrel, rentacoder projects, it won't add a significant cost to the project. If a client doesn't pay, having a lawyer write a letter will take a few hours and cost a few hundred dollars. It doesn't need to be a top of the line lawyer - just being from a lawyer will scare most companies enough to pay the bill. It can probably even be added to the contract that the cost of such a letter is tacked onto the rest of the bill if it needs to be written. This kind of thing is a regular cost of business, and the companies that are likely to cry about the tiny extra costs are often the same companies who won't pay on time. In other words, having the contract done correctly helps preemptively solve the problem of clients not paying.
For number 2: This seems like a reasonable assumption to make for the majority of people reading HN. It's ridiculous to promote a weird, probably illegal, blackmail scheme because a dozen people on HN can't use their court systems.
The better thing to do is have a contract, and if the client doesn't pay, have a lawyer send a threatening letter warning them about contract violations and court action. That should work almost every time, and if it doesn't you'll already have a lawyer familiar with the situation.
For bonus points, have the contract gone over by a lawyer before signing it in the first place. There are law practices and legal services businesses that specialize in it and it only costs a few hundred dollars. And it can be added to the cost of the project.