The DLLs we provider are not strong named to prevent any issues with developers who are using older versions of Visual Studio or projects where this would cause a problem. You can use the project we provide though to build strong named versions of the DLLs by following these simple steps from Microsoft to do so:
It should only take about 2-3 minutes to set up and then you'll just need to build the project one additional time. The output DLLs will now be strong-name signed and you'll be all set to build your managed applications using these DLLs.
Dave Berard Senior Product Manager, Constant Contact