the rate limit can be per username/per ip address/per time period (you receive one notification once every 10 minutes), or a combination. Yes, when you have a

the rate limit can be per username/per ip address/per time period (you receive one notification once every 10 minutes), or a combination. Yes, when you have a botnet of a few thousands computers you could DoS someone. But with that in hand you can also DoS every web service on the internet (with a few exceptions)