Rereading the Guardian article about Elgg, I'd forgotten this detail, which is true:

The idea was conceived in late 2003, when Ben Werdmuller and Tosh were working at Edinburgh University developing e-learning and e-portfolio systems. Werdmuller (an avid blogger) persuaded Tosh (who had just started a PhD in e-portfolios) to start a blog of his own to support his studies. Within a week, Tosh had received comments on his blog from people pointing him to relevant resources and others bloggers had begun to link to him.

Dave and I shared an office at the University of Edinburgh. He was skeptical about blogging at that point, so what I told him was this: start a blog, post every day, and leave a meaningful comment on someone else's blog every day.

I wasn't sure that it would work, but thought that it probably would. Sure enough, within a week or two, he was part of the global elearning community, and was participating in conversations with its thought leaders. It was through this medium that we put out the initial white papers (completely unofficially) that provided the basis for Elgg, which went viral in the elearning community.

Could that happen today? I'm not sure.