There are a lot of reasons to want to watch a YouTube video simultaneously with someone - such as conversation that doesn't involve constant mentions of timestamps. The simple way to get in sync like that? YouTubeSocial.
YouTubeSocial is a clever little site that allows you to watch any YouTube clip in sync with your friends. All you have to do is either enter the video's URL on the site or alter it to include the word social. (This means that youtube.com/watch?v=3-Bx9_pDF8c would become youtubesocial.com/watch?v=3-Bx9_pDF8c.) Once you've done that, you'll have a link to hand to your friends and a virtual remote that can be passed around to choose who's in control of the clip. As a bonus, there's a chat feature and the option of inviting more people using Facebook Connect.
Sounds easy? It is.