Occupy Underground

Italy's parliament is a mess just as it is right now, with more parties than anybody needs (7 major and 27 minor parties) and a ridiculously low election-threshold of just 2%.

The italian parliament consists of 10 parties right now, including Grillo's, summed up into 4 coalitions. Further fracturing of Grillo's party will double or triple that number.
(Please imagine how fast the US Congress and the US-Senate would be if you go from 2 to 4 parties.)

Don't get me wrong, I'm for a fair representation, but at some point you need the assurance that certain politicians would vote in a certain way. If Grillo really wants to forgo a party-structure, then how is he supposed to get anything done?
If Grillo can't guarantee that members of his own party will accept or reject certain kinds of bills, why should other parties take his support/antagonism into account?
If Grillo's party behaves unpredictable, why should any other party bother to help them reach their goals?

Look at the republican party in the US right now: the Boehner-Rove-establishment (money) vs the Tea Party (ideology). Economic hawks vs Defense hawks. The hatred for Obama is the only thing that keeps them together!
How is such a party supposed to work through the list of promises they gave to their constituents?