A fantastic summary of internet hype from somebody over at b3ta.com.
(Not always the most respectable site in the world - if you browse around and are offended, don't say you weren't warned.)
I'm not sure if I've just come across the Next Big Thing, but this site sort of reminds me of Facebook when I first came across it. Mainly because their friend search says that nobody I know uses it. Facebook started like that when I first scanned my email address book, so I deleted my account and then suddenly the 'join me on Facebook!' emails started arriving.
No current users as evidence of future success. Try selling that one to your bank manager.
I really like the idea of FriendFeed though, because it's not trying to be a host for everything. Let's be honest, Facebook is rubbish at photos and video - Flickr and Vimeo are much better, so what you need is a tool to tell everyone you know when you create anything you'd like to share, wherever it happens to be. This is what opensocial was supposed to do and it's interesting that some ex-Google staff are behind FriendFeed.
Whether FriendFeed is really the Next Big Thing or not, I think its model is the future for the social web. Facebook will eventually die because it's not good at anything except linking you to other people and it's not brilliant at that. What we really need is an engine like the Facebook friends list, that lets you share from anywhere. And it could be FriendFeed.