A hosebibb, such as the outside faucet shown below, has a number of vulnerabilities. First, let's talk about freezing. This is not a frost-free installation. In the winter, water would stay in the pipe not only below ground but in all of the exposed pipe that is above ground. If, in fact, the faucet has a shut-off nearby that not only turns off the water to the faucet but also drains it, then that is one solution. However, it is not a very convenient solution and it is a shutoff that, while there, will probably seldom be used. I speak from experience on that one, having a couple faucets like this one. One way to improve the system, without having to do too much to change it, would be to go to a frost-free yard hydrant. They are more expensive but durable and a much better solution.
This system, below, also does not have a back-flow preventer so, in the eventuality of a low water pressure situation, contaminated water could make it's way into the potable water. That problem, which has to do with cross-connections, can be remedied by installing a screw-on back-flow preventer that fits just above the hose on about any standard outdoor faucet that is in good shape -- not warped, cracked, etc.
Thanks for looking.
Steven L. Smith
Bellingham WA Home Inspections