Should not be able to add different services with the same GUID

[LocalJoost]

If you think you are smart (like me) but really are not (like me) you can make a service for platform A, then proceed for Platform B and start out Service B by copying Service A and adapting the class name, you will end up with two different services with the same GUID.

This has a peculiar side effect: if you try to add Service A, it works. If you try to add Service B, it adds a second instance of Service A.
Although this is a clear PEBKAC, people are going to fall into this trap, and it took me about 5 minutes to figure it out, less experienced Service builders might get stuck here. To prevent support requests, you might want to include some guard rails here.