Most of the above points are MOOT.
@ gmaxwell there is no CENTRAL checkpoint, all bans and checkpoints are done locally and in memory only
@ meta.p02 there are a few attacks that bypass this system, but this system was designed primarily to stop most attacks from being profitable.
@Hazard , Please don't talk about technical skill when you don't possess any.
@BitcoinEXpress Anyone with a significant amount of resources can break virtually anything that relies on p2p communication... this is meant to act as a stopgap measure, and as the number of nodes grow, so does the feasibility of this defense. Remember even when submitting with multiple nodes there will be a convergence point to a legitimate peer, and then that legitimate peer will be banned for transmitting too quickly, thereby segmenting the network for 4 hours but keeping many legitimate users safe.
@User705 Correct, it's possible to sloatboat your way around the system over time, but such an attack would be noticable and thus far easier to prepare for(on the dev side of things).
@ghostlander it's not based on the assumption of a single peer, remember that in p2p networks as the network grows larger there is always a convergence point, it will segment the network for 4 hours before allowing them to continue, the segmentation is limited by how many nodes the attacker controls and is a good defense for a large network.
@QuantPlus We don't post propaganda, perhaps you should look to one of the other altcoins? We've backed up every claim we've made to date.

Stop arguing over semantics, this was designed to stop some double spending attacks, basic difficulty attacks, and multipools(and it does that very well). When I say "virtual immunity" - I don't mean total immunity, I mean immunity from pretty much anyone out there who realizes that the cost of the attack would be greater than the gain.

The system is designed to cut off an affected portion of the network in the event of a multi-pronged attack, they will simply reconnect in 4 hours and continue on the main chain. This may make it unfeasible for something with < 100 nodes, but for bitcoin its perfectly usable.