A bank running a lot of nodes would be like a bank providing services for the competition for free.  Unless that bank makes money off bitcoin in some other way it does not make sense.

By node, OP probably mean miner.

A big pool owner like GHash.IO is a super miner

a super node is simple a known static IP people can add so that they always have a main connection to th network to relay tx's.

now thats cleared up. all i have to say is
1. Banks are contracted to handle FIAT, being a node is meaning less to them. get over it, you wont see banks handing out bitcoins themselves.
2. people can choose which supernodes they connect to. so the end result of any fantasy Apocalypse scenario some tin foil hatter is about to dream up... wont happen as people will just ignore such nodes

So all those fallback nodes here [1] are supernodes? I expected a little more than a static IP and a wiki entry from the "super" prefix.

Well but the more fallback nodes the better, I dont see any problems with banks running nodes.

[1] https://en.bitcoin.it/wiki/Fallback_Nodes

we don't need supernodes.
skype crash regulary because of this (bandwidth hole) ... actually.

all users must be at the same level ... like miners.

Is this meant to merely guard against being 'cast out' of the DNS system? Seems like a fragile solution. Could not an attacker just put up dozens or hundreds -- or even thousands -- of low-cost nodes that implement the same IP?

Less nodes is always a bad thing since it means that Bitcoin is more centralized
Full nodes relay transactions and the decentralized aspects of full nodes are important to keeping Bitcoin transactions confirmed and stored safely

The concern is a decreasing amount of full nodes that relay Bitcoin transactions and that banks will control most of the full nodes in operation
Meaning that all transactions are relayed through their nodes due to mining concentration and the costs increasing to host Bitcoin nodes in time and bandwidth.
At least that is how I interpreted the OP's question hence the banks become supernodes controlling most of the nodes in the network.