scooterdude, if you're starting a brand new directory and have no membership base to begin with, you'll be fighting an uphill battle. I'm sure the percentages of success are below the 2-3% mark when it comes to "new" directories.
In this instance, we already have a membership base. This is being utilized to promote additional benefits to the active and inactive members. There's a long list of pros in doing this. The main one is that we're creating our own community of members and we're going to take them to the next level of their practices - online. :)