The TTL on the A record for youtube.com is 5 mins though, so a "well-behaved" client would likely need to re-query the DNS. You could just edit your local host

The TTL on the A record for youtube.com is 5 mins though, so a "well-behaved" client would likely need to re-query the DNS. You could just edit your local hosts file to circumvent that but you'd have to then have entries for the myriad of streaming servers that YouTube uses to deliver videos.