Yes, anything and everything that might "accidentally" fall into or touch any part of the build not intended to be touched or fallen into that would normally be protected by the enclosure panels of a normal case.
If you have pets, of any kind, kids, of any kind, or EVER have food or drinks within ten feet of your PC, then having an open or test bench case/mounting is a very bad idea.
If you are not incredibly careful, and by that I mean you are not in ANY WAY clumsy, lack of attention or accident prone, then having a test bench is a very bad idea.
If the room where your hardware resides is carpeted, then it is a very bad idea, because you will inevitably walk across your floor at some point and touch something in your build without discharging yourself on something else first, and zap something.
In general, for 99% of people, this is a bad idea. For the other 1%, they would not even be asking this question.