I too came across such a requirement. @Dmitriy : here is a clear example u asked for.
My house has 3 rooms, each with 3 conventional switch boards. All the rooms have a fairly similar electrical layout. Now i plan to automate/control them with Blynk.
I would wish to use an esp12-E for each switchboard. So I would end up using 9 esp12-Es divided into 3 rooms/tags. My app would have a device selector that would be capable of selecting tags, buttons that correspond to switches and sliders that correspond to fan speed regulators.
Now that would work as intended. But there is another way of doing it. Giving all controllers the same auth token, using a menu and program accordingly. But what if I would want home screen buttons for switches that I would go for often when I enter rooms( like the light buttons). I can't guess or change the active menu item on the app frequently when i are running out of time and am searching for my car's key.with separate auth tokens for controllers I'll make a quick control panel of buttons and add them to the home screen.
I have already finished the software side of the project and have implemented it in one of the rooms and is being tested. Using Bridge adds a lot of data traffic than esp could handle and it often disconnects due to data flood error.