"Flawed..."? Maybe. But it is so because Diamandis presented a plan originally created by Talmon Feuerstein in 2003 while a student at ISU. Feuerstein's thesis (called Mars Citizenship Program!) can be found here:
http://library.isunet.edu/Main.htm&folder=-0026+%80+
Student+IP+reports&Range=0003
I have known of the program for two years now, I also know that Feuerstein realized that the original scheme was not quite workable yet, and that since then apparently he came up with a better solution. As far as I can tell, Diamandis's presentation was based on the original scheme, using the figures from the thesis, while Feuerstein's name did not seem to have been mentioned at all.

Right now Mr. Feuerstein is the vice-president of a German company, NSD-Fusion GmbH,
(http://www.spacenow.ca/index.php?page=home&nomax=1)
and I am kinda wondering whether he is aware of
Diamandis's presentation at all... ;)