Someone on Reddit recently dug up this email from the early days of bitcoin development, from Satoshi Nakamoto (the founder of bitcoin).
He anticipated this problem and foresaw that eventually only specialized hardware would run full nodes, and everyone else would run on a highly simplified system requiring a lot less bandwidth/storage.
"Bank" carries a lot of unfortunate connotations with it that won't necessarily apply to the supernodes. It would be better to use a different term for those.
What's likely to closely resemble banks in the future are bitcoin clearing houses, where transactions just move around internally. These will be supernodes themselves, but not all supernodes need to be this kind of clearing house.
He anticipated this problem and foresaw that eventually only specialized hardware would run full nodes, and everyone else would run on a highly simplified system requiring a lot less bandwidth/storage.
http://www.mail-archive.com/cryptography@metzdowd.com/msg099...