Via Tyler Cowen, a must read from Paul Mason:
What caused Mr Papandreou's sudden move? Even some of the MPs closest to him had no idea it was going to happen.
Many of my Twitter correspondents suggest it was the vehemence of "Oxi Day" last week, leading to clashes between parading soldiers and protesters and local Pasok politicians getting hounded off the parades.
Pasok remains a very well rooted social democratic party, with multi-generational networks inside every village. If the village guys start ringing up and saying - there is no way we can hold it - Mr Papandreou is politician enough to hear this.
Another potential reason is capital flight. Anecdotal evidence suggests that the Greek elite are buying up property in London just as fast as they can find berths in Poole for their yachts. They are voting with their spinnakers, on the basis that the game is up. In any future Greece on offer, they will have to start paying taxes and they do not want to.