Total of unique bitcoin address doesn't reflect whether bitcoin will fail or not. If we talking whether bitcoin will fail or not, we should see actual bitcoin adoption, acceptance and scaling/upgrade instead.
Why do the number of addresses fall every now and then? I would assume the graph should have gone up all the time, no? When people lose interest in bitcoin, I would have thought that they would just uninstall their wallet apps or something. Are they deactivating their addresses as well?
I think when the balance is empty, blockchain.info counts it as inactive/used address. Also, deactivating address isn't possible.
I fully support your side of the argument. Unique bitcoin address could be misleading in judging the rise and fall of bitcoins. The reason being that there could be numerous transfers and other factors to that effect; however actual bitcoin adoption, acceptance and ugrading shoud rather be the considering factors