I am going to work on a wcf service that would expose our catalog information for several external organization to access. I would like to authenticate/authorize them using a simple table in my back end which contains their login information. (right now there is only one, but could grow down the line) Should I be using the wcf message with transport credential for this scenario? Any thoughts/suggestions would be welcome. Does it even matter how they access our wcf service? I will be using vs2012.
Given that your clients may not be using WCF or even Windows, I would recommend using WSHttpBinding, which allows you to use message security and attach username and passwords to the request. On your host you can then use a custom password validator to verify the credentials against your database. See http://msdn.microsoft.com/en-us/library/aa702565.aspx for more information on that. SSL is also an additional option if you want the transport secured.