Under Ta'if the speaker gained a four year term of office (as compared to the previous one year term). This means that Nabih Berri is in a strong position to permanently affect the work of the Lebanese parliament.
The additional threat is for members of the Hezbollah-Amal bloc to resign (perhaps in league with the Free Political Movement of Aoun), which would not technically stop the work of the parliament but it would radically reduce its legitimacy.
The Daily Star - Politics - Berri vows to ignore actions of current Cabinet - adviser: "Resigned Parliament Speaker Nabih Berri has said that he would not recognize decisions passed by Premier Fouad Siniora's Cabinet in the absence of the Shiite bloc of ministers, a source close to the speaker said on Sunday. Berri's statement covered a decision Saturday to approve the formation of an international tribunal to prosecute suspects in the assassination of former Premier Rafik Hariri.
Berri 'considers that the Cabinet session Saturday never happened, and he will deal with its decisions as if they never occurred,' Arafat Hijjazi, adviser to the speaker, told The Daily Star in a telephone interview."