Okumura Jun has put up a series of seminal posts over the last few days at GlobalTalk 21. I suggest you check them out.
On the subject of checking out, Okumura-san is correct in stating that Section 4.2 of the By-Laws of the Democratic Party of Japan (Link-J) imprisoning Diet members inside the party until such time as their resignations have been ratified by the Executive Council (jonnin kanjikai) is in abeyance, as the dissolution of the Diet -- which the Emperor, despite the legal and constitutional issues, solemly decreed* -- strips all the House's members of their badges.
So you do not have to die to get out of the DPJ (Link). All you have to do is wait for the Prime Minister (through a dissolution) or the Constitution (through the four-year term limit) to set you free.
So why did eight members of the Diet submit their resignations to DPJ Secretary-General Koshi'ishi Azuma this week, when the Diet dissolution was going to free them to hook up with any party they pleased? For the publicity, of course, but also to humiliate the Prime Minister. It is only fair, for they feel humiliated by him.
The big news was the last minute resignation of Fukuda Eriko (Nagasaki District #1, 1 election to the Diet) the former leader of the Kyushu Plaintiffs in the Tainted Blood Products lawsuit (Link - J). Though incredibly young (32) and a first-termer, she nevertheless commands respect (Link). Her departure represents a huge, though not unexpected, loss for the DPJ and a huge shot of adrenaline for Tanioka Kuniko's Green Breeze Party (Link). As the embodiment of resistance to government intransigence and shirking of responsibility, Fukuda helped make credible the DPJ's pledge to put policy making in the hands of politicians rather than leaving everything to the bureaucrats.
The DPJ, which suffers from the image of being the guy's party (just look at the Cabinet) has lost one of its iconic woman members.
Speaking of prominent women members of the DPJ, Minister of Education, Sports, Science, and Technology Tanaka Makiko is hopping mad at the Prime Minister's decision to call an election (Link - J). She did, as Cabinet member, join in the issuance of a Cabinet Decision (kakugi kettei) ratifying the dissolution of the Diet. From her disparagement of the timing of the dissolution, however, it is hard to imagine her and her husband sticking around.
* It was jarring to hear the Speaker read out the Emperor's Diet dissolution letter. His Highness speaks and writes in curlicues of grammar and euphemism most of the time. The message to the Diet, however, was in the plain form (e.g. - "kaisan suru").