Cases around closure of bank accounts? None that I know of. Incidences of banks closing accounts without giving reasons? Loads. All banks that I know have something similar to this written into their account terms (this is taken straight from CBA's terms at clause 6.4):
"We can close your account at any time after giving you reasonable notice."
There's no need for them to give a reason. Most banks (and all banks I've dealt with on this issue) refuse to give a reason, citing at best that it is a 'commercial decision'. I've seen banks decide to wholesale cease serving an entire industry (notably - Westpac). In these circumstances it generally comes without notice and involves them contacting a business and stating that all their trading accounts, cards, and other accounts for not only the business, but also directors and staff, will be called closed in XX days.
The Banking Code of Practice, in reference to account closure, specifically states (at clause 143): "We may close an account of yours under its terms and conditions if that account is in credit."
So - not a breach of contract. The ability to close an account is actually written into the contract.