1. Why don't they listen to the scientist when he's screaming, "It's infectious! If you let it out, you'll kill us all?!?!?!"
2. Why, when they ask the scientist what it's infected with, does he give such an utterly crap answer? "Rage." Yes, that'll be nice and convincing to the ALF.
3. Why don't the infected attack each other?
4. How does the virus spread, given that anyone infected is now mindless, vomiting blood, and probably has severe injuries from where the infected were beating the crap out of him/her? Seriously, these guys would have a lifespan measured in minutes, hours at best. Even if we were talking "starved to death" (and it'd actually be dehydration, since they don't drink either,) it'd be no more than a day. And again--vomiting blood.
5. If the infected are nocturnal, why are they attracted to bright lights? (Yeah, OK, moths, but it's still annoying.)
6. How does a coma patient survive four weeks in the middle of an evacuation of London and its degeneration into total chaos?
7. How is it that Christopher Eccleston's character doesn't know that the infection is localized to the British Isles, given that he's commanding a military unit with access to radios, satellite communications, and helicopters? (And his actions in the film only make sense if he truly believes his group is the last outpost of humanity.)
8. How does a recovering coma patient and professional bike messenger manage to take on two or three SAS squaddies in hand-to-hand combat?
9. No, seriously, how? It's like he suddenly turns into Batman for the last half-hour of the movie.
10. ...the hell?