Concept is good, I have tested its working. 

Need to explore for implementation

I'm really glad to see this is being received well.  The code snippets got reformatted a little, so I apologize if hard to read;  this is my first article & I have lot to learn about publishing in HTML.

We just reviewed this with our development team and they made a great suggestion which we've adopted as our standard approach, and that I wish I'd included in the original article:  write custom "encrypt" and "decrpyt" UDFs for each encrypted column.  These make subsequent coding much simpler, developers don't have to know names of the symmetric key or the certificate, don't have to worry about casting the datatypes, etc. 

create function dbo.fnEncryptAccountNbr(@AccountNbr varchar(16))
returns varbinary(68)
as
begin 
        return EncryptByKey(Key_GUID('MyKey'), @AccountNbr);
end
go

create function dbo.fnDecryptAccountNbr(@EncryptedAccountNbr varbinary(68))
returns varchar(16)
as
begin 
        return convert(varchar(16), DecryptByKeyAutoCert(cert_id('MyCert'), null, @EncryptedAccountNbr));
end
go

I have only tested this a little bit, but so far don't see any performance hit caused by these UDFs (I've been badly burned by UDF performance--or lack thereof--in SQL2000, am always on guard for that now). 

Forgot to include this:  in addition to the UDFs, we've also decided to use a stored proc to wrap/hide the open symmetric key business. 

create proc dbo.spOpenSymmKey
as
--open symm key if not already open
set nocount on
if not exists(select 1 from sys.openkeys where key_name = 'MySymmKey' and database_name = db_name())
        open symmetric key MySymmKey decryption by certificate MyCert;
go

PS - Would have been cool to embed this functionality in the fnEncryptxxx UDF, but cannot because it causes a "side-effect" and SQL won't let you.