Why does a mask hide you on one night and expose you on another? On Halloween, a man in a rubber werewolf mask can walk the length of a crowded street and nobody remembers him. Hundreds of other people are wearing masks too. Three days later, that same man wears that same mask into the grocery store, and every shopper in the building could describe him to the police. The mask is the same. The crowd around him is gone. Privacy works like that. A hiding place is only as good as the number of people hiding in it with you. People who study this call that number the anonymity set: the group of people who all look alike to someone watching. Bitcoin keeps a public record of every payment. Names are left off, but anyone can follow coins from address to address, and addresses are the account numbers on that record. One way to blur the trail is a coinjoin, where many people combine their payments into one transaction so an outside observer cannot tell whose coins went where. Ten people in a coinjoin give each of them a crowd of ten. A thousand people give each of them a crowd of a thousand. So here is the question I care about. Does a privacy tool protect you, or does it point at you because so few people use it? The worry deserves a fair hearing. Coinjoins have a shape you can spot, so the transaction itself can stand out like the mask in the grocery store. Some exchanges flag coins that went through one. Tracing firms also watch for slips after the mix, like spending those coins together again, which shrinks the crowd back down. There is another side. When a privacy feature becomes the default, everybody wears the mask. The 2021 Taproot upgrade let many different kinds of spending look alike on the record, so a simple payment and a complex payment can wear the same costume. Wallets that build privacy in without asking pull in people who never thought about it, and those people are the crowd. Here is how I would know I am wrong. If default privacy features spread across most wallets and tracing firms can still match most payments to their owners just as easily, then crowd size protects people less than I think. I have used Bitcoin since 2015, and the first thing I check in any privacy tool now is how many other people use it. On Halloween you are hard to spot because everyone came dressed up. If this changed how you look at privacy tools, Zap ⚡

What does it cost to keep a jewelry store safe overnight? A jeweler on a small town main street rolls down a steel shutter, checks the cameras, and pays a guard every night to sit in a car out front until morning. When the case holds a few silver rings, a lock is enough. When the case fills with diamonds, she adds the guard. Her security bill grows with what sits behind the glass, because a thief does the same math she does. Bitcoin has a guard too. Miners are computers spread around the world that bundle payments into blocks, the pages of a shared record. To add a page, a miner has to burn real electricity solving a puzzle, a method called proof of work. Rewriting old pages would mean outspending every honest miner at once. That spending is the shutter. Someone has to pay the guard. Today most of a miner's income is the block subsidy, new coins the network creates with each block. About every four years that subsidy is cut in half. It went from 25 coins in 2012 to 3.125 in 2024. The rest of the pay comes from fees, the small amount each person adds to get a payment into a block. So here is the question I keep coming back to. As the new coins shrink toward zero, will fees grow enough to keep the guard paid while the case keeps filling up? The worry deserves a fair hearing. Fees have stayed a small slice of miner income in most months. If people move most everyday payments to faster layers built on top, fewer of them pay fees on the base chain. A cheaper guard in front of a fuller case is the setup a thief waits for. There is another side. Those top layers still settle on the base chain, and big settlements will pay well for a spot in a scarce block. The coin's value has also grown faster than the subsidy fell across past cuts, which kept miner pay in dollars climbing. Here is how I would know I am wrong. If over the next two halvings fees stay a tiny share of miner income and the total computing power securing the network falls for years in a row, the guard is getting cheaper while the jewels pile up. I have watched this since 2015, and these days I check the fee share of each block more often than I check the price. A shutter only works while somebody keeps paying for it. If this gave you a new number to watch, Zap ⚡