Okay, pick one? Or use both interchangeably? First, maybe we'll define them since they're relatively new buzzwords (memes?)
Presence Stream - used by the social-networking/microblogging site Jaiku, where you can not only post short posts, but also supply RSS feeds which will be added into your list of posts, thus creating your presence stream.
Life Feed - I first heard this from Steve Dembo on Teach42's Podcast as a feed which includes ALL OTHER feeds that you own (Twitter, blog, Flickr, Facebook, and so on).
I haven't gotten to the point of wanting to combine all my social-networking/Web2.0 sites, but I'm definitely interested in sharing my Twitter feeds and such. I've posted about identity online, and separating professional vs. personal identities...but here's my Twitter account: http://twitter.com/ipendakeynes.
You noticed: it's not my real name. It's actually my Second Life avatar's name. As I begin to use Second Life more for educational/research purposes, I feel more comfortable sharing my Second Life with my real life contacts. Most importantly, I'm not afraid to do so anymore.