Maybe something you should be aware of, when discussing the electoral wing: The Italian Five-Star-Movement has used such an architecture before. While the participants of the movement use a similar website to DiEM25's, that is — without the slightest transparency regarding the correctness of the voting process (see http://my.pages.de/dcentyrprirousseau for more details on "Rousseau") — in order to legally partake in elections and receive electoral funds, Mr Beppe Grillo, the owner of the logo and thus the entire movement (if he doesn't like your political activity, he can simply expel you by saying you're not allowed to use the logo and act in the name of the 5 Star Movement — he has kicked out dozens of persons that disagreed with him in the past years), registered a political party with only three members: his nephew, himself and his tax accountant, if I'm not mistaken. I wrote some more about it on http://my.pages.de/wfd2013.
Why would someone do that? Well, it is intended to bypass the legal restrictions of parties and assert a movement that does not guarantee the same minimum degree of inner democracy. Party legislation was conceived by reasonable people who want to make sure no "populist" movements arise which disenfranchise their members. Legislators aren't keen on creating bureaucracy, what they wanted is to make sure that the participants of a political association or party will always be able to exercise democratic powers.
The way the Movimento Cinque Stelle and DiEM25 are architected, the democratic powers of participants depend on the good will of the leadership. They are full of best intentions but structurally undemocratic because it is part of the definition of democracy that it MUST NOT rely on trust and good will towards anyone. Beppe Grillo's electoral wing therefore is a method to bypass legislation that would guarantee basic democratic rights to his supporters.
DiEM25 already has a similar architecture in its founding documents. The Organising Principles describe the existence of a legal entity, a non-profit association registered in Belgium. This association has to comply with requirements of traditional representative democracy, therefore its members have more inner democracy than DiEM25 itself. We know representative democracy isn't ideal, but it should only be bypassed for an architecture that offers more democracy, not less! The members of that association are the same people that form DiEM25's CC, says the document, and they pledged to not exercise their democratic rights but rather obey to whatever DiEM25 decides — which would be totally fine if DiEM25 itself was reliably democratic. Instead, technically, it is a webmastercracy.
Don't get me wrong, there is no reason to assume anyone is acting in bad faith. The leadership of DiEM25 may think it is okay to introduce a dependency on trust in exchange for a different governance model than the traditional representative democracy which has failed us so frequently before. But the point is, it is not necessary to impose lack of transparency on the DiEM base, we can do better with a fully transparent Permanent Assembly. Whereas tricky structures to bypass legislations are risky. If Beppe Grillo has abused them, even though he is the nicest chap and we all loved him on Italian television, how can we expect everybody else to be immune to the lure of absolute power?
So, my conclusion is: the electoral wing is a side structure that introduces the risk of detaching democratic rights from the movement. We should first ensure that the movement is truly bottom-up democratic and accountable in its voting procedures, then there is nothing wrong with the movement taking a bottom-up decision to partake in electoral contests. If you are afraid of DiEM25 becoming a party, I warn you that it currently is formally less democratic than any democratic party. And it totally depends on good will if a formal deficiency becomes a factual one.