I mentioned it in a earlier post, pull is in nearly all situations better than push. Ross seems to share this view in The Cost of Presence:

Heck, the most efficient ways of communicating rich presence is asynchronous (blog posts, Flickr, Plazes) and yet to be integrated -- there is no Xfire (* see below) for real worlds.

When you factor in the rise of RSS as a Pull mechanism that the receiver controls -- there is a significant shift underway to make senders pay. If you don't write a worthwhile blog post, people don't pay attention.

He also speaks about the privacy issue in regard to cellphones:

When cell phones capture and constantly transmit spatial presence we may be in for the biggest privacy shock of our time. Like a camera over our shoulder, only it's in your pocket, everywhere and nearly always on. Social norms will significantly evolve.

Here I would be interested to know who asians countries do handle this. They have GPS-enabled phones since around 2003.

* Xfire and Persistent Presence

Xfire takes this to the next level. It creates a profile about a user actually does, and allows others to see it. Imagine if you will, running a piece of software that watched what you did online. It could tell where you spent your time online and what you were connected to currently. If you were in an IRC channel, it could point your friends to the IRC channel. If you were posting a lot on a specific message board or wiki, it could tell your friends that's what you'd been up to recently.

Couldn't we consider that Audioscrobbler is going into this direction?