Sorry, in Finnish:
http://harto.wordpress.com/2011/05/13/loysiko-suomalaisopiskelija-bloggerista-tietoturva-aukon-vahingossa/

via http://www.mikropc.net/kaikki_uutiset/suomalaisopiskelija+kauhistui+kaatoi+googlen+verkkopalvelun+vahingossa++quottoivottavasti+poliisit+eivat+ole+kohta+ovellaquot/a626264

[Blogger]....

It's working now:
http://buzz.blogger.com/2011/05/blogger-is-back.html

Language switch:
http://thefinngeek.wordpress.com/2011/05/13/finnish-student-manged-to-take-down-blogger-by-accident/

So, was it a bug or a hack?

Difficult to say, or Google doesn't want to disclose the actual reason.

See
http://news.netcraft.com/archives/2011/05/13/blogger-maintenance-causes-extended-outage.html

http://mobile.twitter.com/Blogger/status/68823593877913602

Any opinions about that?