Why someone is mining there in the first place: - A website author can include a script for their _users_ to mine coins for the website author, which effective

Why someone is mining there in the first place: - A website author can include a script for their _users_ to mine coins for the website author, which effectively distributes work across many machines you don't own. - This means, instead of mining on just your own machine, you're effectively mining across N machines (however many users you have) as long as they have your website open (at a ~60% efficiency rate according to other comments). - This is great for the website author, as it's very little effort on their behalf for a small profit, and affects each individual user less than the whole. Why someone would want to block coin miners: - Mining is very CPU intensive, which can slow down the browser for users. - Increased CPU usage can also lead to higher electricity bills - Increased CPU usage can also lead to lower battery life - Someone might also not want to benefit the owner of a website they're visiting, especially if it's at any cost to them (electricity bills, battery, cpu, etc)