This is yet another example of someone whose life revolves around the "social media" echo chamber having next to no idea how regular people use the internet. Gillmor might use dozens of nearly-useless social networks and thus think that "the stream" is overtaking email, and he might assume that this is a common problem because Robert Scoble and Dave Winer agree with him, but I don't think that regular people, whose lives don't revolve around the never-ending churn of new social networks and new gadgets, would agree in the slightest with almost anything he wrote. They probably wouldn't even understand what exactly he was talking about.
Sure, in the mainstream Facebook is definitely starting to take the place of email, but I don't think that's more of a product of convenience than it was a product of people being overwhelmed by "the stream". I mean, seriously:
"What happens now is that these stream objects are lit up with transactional properties. Code gets run based on incoming events, pulling it out of the teeming inbox before we see it and converted into actions predetermined by our inference engines and workflow rules."
That sentence describes the workflow of maybe 0.1% of the general population. Commentators need to look outside of the echo chamber once in a while before declaring that Google needs to change course because it doesn't fit their extremely niche needs.