It just depends whether you want to be able to borrow money in the future. If you think you've currently got a good lot and have a stable, self-sustaining economy then fine, default.
http://icelandreview.com/icelandrevi...7862.news.aspx
Even if the credit raters upgrade Iceland in a couple of years to non-junk, it will never again achieve a high enough rating to borrow money at a decent rate. Furthermore, bankruptcy can leave you with legacies if it breaks other agreements - I believe Iceland still face the prospect of being thrown out of EFTA if the ESA court finds against them, which could do significant harm to their economy in the long run.