Official blog of FriendFeed, the social aggregator acquired by Facebook, covering product launches and the Simple Update Protocol.
HN cites it as evidence FriendFeed launched the Like button before Facebook, and for its Simple Update Protocol argument on why RSS is slow.
FriendFeed is part of Facebook though?
http://blog.friendfeed.com/2009/08/friendfeed-accepts-facebook-friend.html
You might be able to take a user's data to establish their profile, they consented by using your application after all. But I don't think you can export their friend list and use it to invite them to your new social network.
Either way, I think Facebook could find something in their ToS to shut you down if they feel like you're stealing their users away. There was a recent article about a tool from Power Ventures that allowed you to login to multiple social networks and aggregate the messages, friends lists and what not. Facebook seemed to claim it was a violation of the ToS because they were accessing account data using "automated means."
http://www.eff.org/press/archives/2010/05/03
If you read about FriendFeed's Simple Update Protocol (http://blog.friendfeed.com/2008/08/simple-update-protocol-fetch-updates.html), you'll find some good arguments about why RSS slow. The crux of the problem is that to get any updates on a feed, you have to request and download the entire RSS feed (which is filled with summary text and is of nontrivial size).
Consider the case of a real-time news aggregator. A news source doesn't update very frequently (say once every 5 minutes), but you want to provide updates super fast (say within 30 seconds). That means on average you have to scrape the entire RSS feed 10 times for a single update. On the other hand, FB/Twitter APIs give you the flexibility to do things like "download items after this id," which hog much less bandwidth.
FriendFeed's introduction of the original "Like" feature. "Like, ten years, today!" https://twitter.com/paultoo/status/925052780263358465
Facebook added a "nearly identical" feature in February 2009 [0], and acquired FriendFeed about 6 months later [1].
The FriendFeed post is still up, but I shared this archived version which also retains a screenshot [2].
[0] https://techcrunch.com/2009/02/09/facebook-activates-like-button-friendfeed-tires-of-sincere-flattery/
[1] https://techcrunch.com/2009/08/10/facebook-acquires-friendfeed/
[2] http://blog.friendfeed.com/2007/10/i-like-it-i-like-it.html
The news article and the blog post miss a big point that only became apparent to me through Taylor's comment (1): SUS allows services to collect all the individual user update IDs into one file, allowing--for example--FriendFeed to just check <flickr.com/.sus> rather than doing HTTP HEADs on thousands of Flickr feeds.
1: http://blog.friendfeed.com/2008/08/simple-update-protocol-fetch-updates.html#c8777383959063376599
He may have created the icon, but the like was invented and released by the team at FriendFeed about 18 months before Facebook copied the feature (in Feb 2009, the article you linked got that wrong).
[1] http://blog.friendfeed.com/2007/10/i-like-it-i-like-it.html
The problem is that you still need to poll every single feed. SUP allows you to instead poll a single url. See the "update" note at the bottom of http://blog.friendfeed.com/2008/08/simple-update-protocol-fetch-updates.html for more details.