SixApart has just started the Relationship Update Stream service. It's a "friends added and dropped" realtime update feed. It's neat and powerful and useful, and is can do a lot of powerful and scary stuff.
It's also a firehose, that will overwhelm any non-datacenter grade network connection and cpus.
There is value in filtering it and digesting it.
Fortunately, there is a way for mere mortals to get access to that grade of connectivity. Use EC2 and the rest of AWS
You're going to be hit with that firehose which will cost you AWS bandwidth charges, so be ready to monitize your service as fast as you sanely can.