Just had a client tell me their VOIP system is down after a power failure. I saw the machine was not responding (remotely) so I asked that they check to ensure it is turned on. While waiting for their response, I checked a couple of times to see if it has been turned on. When I picked up that the server responded to my pings, I quickly fixed a couple of settings both on the VOIP server and on the trunk configuration to make it work again.

I sent an email to the client telling them I fixed it and it should be working. Client tells me that they turned it on and it is working, implying that that was the cause of the problem. So they never realized that I put in real work to make it function properly, that turning it on was merely a small step in the whole process.

Point is - being too efficient many times bite you in the foot when it comes time to explain your bill to the client.