In normal portrait circumstances, as long as cords are routed to prevent tripping, and light stands are sandbagged if necessary, depending on the environment and lighting modifiers being used, you’re pretty safe. Our main goal is to eliminate all potential for personal injury, or equipment damage.
Break it Down
I’ll admit, the latter hasn’t always worked out for me! Umbrellas create quite the sail on the top of a light stand in even the slightest breeze, and I’ve even experienced a sandbagged beauty dish being toppled by freak gale-force winds. Fortunately, the Canon and Paul C. Buff lighting equipment I use has proved to be quite resilient.
Alien Bee 1600 after falling over backwards with beauty dish from atop a 10' light stand. Light still worked fine!
The beauty dish required some tender loving with a mallet to work her back into shape!
Higher, Baby!
We encounter a new realm of safety requirements once we multiply the ~10′ max height that most light stands provide us by ten. I’m talking about arena catwalks. I cover a lot of events at the Wells Fargo Arena, under my Picture Iowa brand. Events, concerts, sports, etc. I’m currently the team photographer for the Iowa Energy basketball team, and cover their games for NBA Entertainment / Getty. Even though the area is lit extremely well for what it is, the lighting still leaves much to be desired, especially at the shutter speeds required for freezing fast sports action. So, for many events, I will install as set of strobes in the catwalk, approx 100′ above the arena floor.
Don’t Be Insecure
All equipment is safety cabled, in case any of the mounting points were to somehow fail. The absolute last thing we want is 5 lbs of equipment free-falling onto the fans below. With the safety rigging, the furthest anything could drop is a foot or so.
Set of Alien Bee strobes wired for catwalk installation. Two B800 and 2 B1600's shown, along with Pocket Wizard TT1 and TT5 radios. These are the sync cords shown in a mocked-up setup, not safety cables 
Eye bolt installed through the umbrella holder for attaching safety cable
Safety cable routed through the eye bolt, ready to be attached to something sturdy
Throw That Light
The reflectors used on the strobes are larger than used in portrait situations. This focuses the light into a much narrower beam, so that the light is more concentrated and powerful at the location where it hits the floor. I won’t go into the details of how the amount of light reaching the floor is exponentially reduced as the distance increases, I’ll just say that due to the long distance, we need to harness all the power we can get.
You Said You Were Safe!?
One element of safety often ignored when mounting lights up high is a plexiglass shield covering the end of these large reflectors. This shield is to prevent the falling of any glass in the rare circumstance that a flash tube or other bulb should somehow break inside the unit. You’d think something like that could never happen though, right? Wrong!
Flash tube, completely gone! Notice two of the 3 holes still have the post from the flush tube inside!
What The Deuce!?
I recently encountered a situation where the flash tube actually entirely separated from the flash unit! Yes, the bulb completely fell out during use! This is one of the most freak accidents I can imagine happening under these circumstances!
Upon closer inspection, you will see that two of the posts that mount the flash tube into the unit, actually broke off from the bulb, and then the third post pulled out of the unit. Looking at the posts that remained inside the unit, and comparing with another tube, it almost would appear as if the bulb got hot enough to melt a solder joint!
Strobe partially disassembled to remove the flash tube posts. One has already been removed in this photo. The remaining post was practically fused into the hole.
All that remains of the failed flash tube
A good flash tube, for reference. The two posts you see on the right are what separated from the failed unit.
It’s Your butt
I wouldn’t go so far as to say you should install safety shields on all your lights when working with bare reflectors or umbrellas in normal portrait situations. Just be careful of their placement to keep clients, guests, etc clear of your gear. But, if you’re mounting equipment above where other people are sitting/walking/whatever, be sure to employ every last bit of safety equipment possible! It’s way cheaper than a lawsuit 
