According to the SSNVS service information, you are supposed to only use this information for correctly completing IRS W-2.
Verifying the SSN using that service for banking (as I'm reading it) is a clear violation of the system.
Reference (http://www.ssa.gov/employer/ssnvshandbk/ssnvs_bso.htm)
If you were using a different service I'd be interested, as we are always looking for new ways to do validation of accounts.