Be Careful when you add Shared Circles to your existing circle
Shared Circles can be a boon but it may disrupt your circles if you are slightly careless
What If someone shares a Circle full of some unknown users mentioning that it was a photographers circle and you instantly added them to your existing photographers circle.. all you effort creating photographer circle till now will be ruined with 250 more users who may not be photographers at all.
Adding a Shared Circle to your existing circle is like extracting a zip file content directly on to the desktop. You can imagine the mess it can create if the items are not related and will require a lot of effort on your part to re-organize.
My advice is not to add any of the shared circles to existing circle but to create a new circle and park it there until you are sure that those circle users are actually who they claim to be..
You can always move them across the circles internally later on.