With the passage of the Employee Rights under the National Labor Relations Act couldn't all banks become unionized since most if not all banks are required to carry FDIC insurance? Or is there an exemption?

There has never been a prohibition against bank employees forming a union.

In fact, there are some in the Seattle area that I know of.

I worked at the National Bank of Washington (DC)in the 70's. They were owned by the UMW( united mine workers) and the employees (+ or - 600) were members of the OPEIU (office and professional employees international union). I was a member of the management negotiating team (HR Officer at the time)and let me tell you it was an experience, especially when the employees called a strike vote, because they didn't like the terms their committee agreeded to.

So, banks ARE required to post this new notice??

Yep - if you have any federal contracts (take TT&L payments, sell savings bonds, etc.).

According to ABA, if you are FDIC insured you have to post it.....

Yes -- Must be posted.

Posted where?

Cites and more info is on the bank signage tool which was updated recently.

http://www.bankersonline.com/tools/tools.html