Little Brother's title is a total homage to George Orwell's 1984, and to its character/symbol Big Brother. Big Brother also inspired a few reality shows; we're pretty sure we'd rather read Doctorow's book.
Instead of a single "Big Brother" that's watching everyone, the Xnet is filled with many "Little Brothers" who "watch back against the Department of Homeland Security's antiterrorism measures, documenting the failures and excesses" (14.101).
Clever, huh?
We also think there might be commentary on little brothers here: flesh-and-blood little bros can be annoying, never leave you alone, and try to get all the attention. Sounds like Little Brother's DHS, that's for sure.