This is no news at all, as it happened on April 4, but it is still interesting: the organization Adventure Ecology decided to flood several parts of Second Life for a few hours, to show the (not-so-future) effects of global warming.
Tokyo, Amsterdam, London, and the entire Mediterranean island of Ibiza went under,

although the in-world people would quickly get organized with boats, swimming suits and swimming scripts, watch video on YouTube.
Interesting enough, I am hearing from one of the organizers that the event affected mostly press, while Second Life inhabitants didn’t pay that much attention. I wonder how many other media-activist actions are being performed on Second Life; there is a lot of activism around there indeed, but mostly related to First Life politicians ( Democrat John Edwards’s campaign, and the Front National, french extreme right party (what are THEY doing in SL?!), below you can see some reactions) 
) I wonder if this lack of activism from “engaged” members is because of the in-world demographics (not so many engaged members, maybe?) , or simply because I don’t know more about it.