That the students could own their own learning environment. Weblogs of whatever platform, maybe a set of wikis, a social bookmarking service, a Flickr account. I see all these things working quite well. But how to collect and present the relevant information in coherent, even meaningful ways? Some students who have tried the "small pieces, loosely joined" approach to online learning have complained of information overload and and a lack of organization.
So...
RSS and content filtering should make this easy, Stephen Downes had something like this years ago...
But the dream eludes. Might recent advances in mash-ups hold the key?
Built: http://aggrssive.olt.ubc.ca/ Needed content filtering, but that created serious performance issues for http://aggrssive-beta.olt.ubc.ca/
Human Rights in Latin America: Using http://aggrssive.olt.ubc.ca, http://feed2js.org, http://blogsearch.google.com, Technorati tags -- dynamic but rough
Carnival of Gayatri Chakravorty Spivak: Using aggRSSive, Technorati, but mostly http://del.icio.us
Yahoo Pipes seemed promising, but familiar problems emerged.