(S) said:
Huh. What portions of the Aeneid were critical to Augustus? They teach us here that the epic was to Augustus's benefit; it provided an epic past for the Romans [one-up'ing the Greeks at every turn]. It was said that Virgil begged his friends to burn it, because it is incomplete, and Augustus, his patron, ordered his pals not to burn it.
Apparently, the key is the scene where Aeneas is given a sheild in book 8. Some scholars have pointed out that the fact that the shield only depcits war, and the line (in my prose version, but I understand it's similarly translated in other books- last line of book 8):
Marvelling at (the shield), and rejoicing at the things pictured on it without knowing what they were, Aeneas lifted on to his shoulder the fame and the fate of his descendants.
Virgil,
The Aeneid, New Prose Translation by David West, 1991, Peguin Books, England
This last line was apparently a criticism of Augustus's habit of making war without appreciating the horror and sorrow that goes with it. A certain modern-day leader comes to mind.
Now, this is all a bit of a stretch, to be sure, but the argument presented is that Virgil had to slide a criticism in without Augustus noticing. His clue was the last line of book 8- because the last line was supposed to be really significant.
I like to go with this theory, because in repressive regimes, or regimes where strict censorship is practiced, people tend to tightly disguise their criticisms. Look, for example, at Dante's Divine Comedy.
Edit: Or even look at Nostradamus, and how many people even today think he was a soothsayer rather than a critic of his times.