If there is any social application that needs "the real time web", and yet, nobody yet is getting it right.
Let's look at Foursquare.
If I have it write to Twitter, then all my followers, independent of their location or interest, get spammed with my location. (Which is why I've stopped having it do so by default, and instead just push to Twitter for specific cases).
And yet if I don't have it write to Twitter, then people have to poll the website or API, to see where I have been, but they don't get alerted to where I actually am.
Neither of these are good or useful, especially if one has a lot of microblog followers, and more than a very few followers and followees on 4sq.
Spam is bad, and polling is bad.
A better way would be for me to add "email@example.com" to my chat roster.
And then when someone I follow checks in, and they are near me, I would get an IM from that, saying "Bob Smith is at Joe's Bar".
And for me to check in, I send a message to firstname.lastname@example.org, saying either "checkin" or "checkin Remedy" or "checkin 32417", and it will use geo IP lookups, XEP-0080 data, FireEagle data, Google Latitude data, my past checkin history, the checkin string hint, or the actual venue id, to figure out that I am at http://foursquare.com/venue/32417
People who want to see where I have been can just poll the RSS/Atom feed of my checkin history. If that Atom feed implements PubSubHubBub, they don't even need to poll it.