The reason why this joke is apropos to the discussion of power over ethernet is that just because a switch has available ports, does not mean it has enough juice to power all the devices connected to it.
Two failures happen when implementing a solution:
1) Specification for the configuration was fine but people swapped a switch that could have done the job for a cheaper model that couldn't.
2) People add cameras to a switch without fully under standing the power loads demanded independent of the network traffic associated with it.
The ultimate problem is that POE issues are hard to diagnose if you don't have the right diagnostic experience and tools. This is because various devices may not pull a constant amount of power. Motors, heaters, in addition to the other electronics may vary the power demands, peaking in short cycles that are significantly higher than normal cycles. Like when you start your toaster when microwave is running, everything is fine until the refrigerator's compressor kicks in and the whole kitchen goes dark. You notice these events right away because you probably have to go flip the breaker to get the lights to come back on. However, for surveillance networks, a switch may power-fail a port when peak loads are beyond its capacity, but it is able to handle its connected devices at other times and cameras reboot. One might never see the cameras go offline unless you were physically watching that video feed at the moment it lost power.
What is needed, minimally, is a system, like Viakoo, that tracks the cameras recording uptime and alerting you when these cameras and their associated recording streams go down that you can even be aware that you have a problem. In the Viakoo system, you may see this as a "Flapping" camera (i.e., a camera that goes up and down more than 2 or 3 times in a 24 hour window. More intermittent failures might show that, though the camera doesn't go up and down more than once a day, it will show up on your operations report several times over the course of a week or month.
If you also configure a Managed Switch in your environment, the associated port data for that camera should also show incrementally increasing POE events (e.g., Overload Counts, et cetera). You can confirm this by looking at the overall power-load of a switch. With Viakoo, not only will we open a ticket when these events occur, you can view all these measures and correlate it to your stream offline events to validate for yourself that, indeed, you have a power problem.
In summary, without Viakoo, POE problems often go undetected and are difficult to diagnose. If you have streams with periodic recording gaps or cameras that mysteriously rebooting, you may have POE problems. Viakoo can detect these failures as they happen and, if you add your managed POE switches into your Viakoo configuration, you can determine more definitively that this is what is happening.