Growing up we were always taught to never step straight over a rock or log because it is a good way to step on or startle a snake that you cannot see. However, on a lot of hiking forums I see it advised to never step ON a log or rock due to the risk of losing your footing and falling.
Which is the better practice and why?
This is one of these subjective topics where there's advantages and disadvantages both ways - I've seen people that will religiously advocate either one of these approaches in all scenarios.
I'd personally scrap both those hard hit rules however and instead promote a knowledge of the advantages and disadvantages of each, and an awareness of the surroundings allowing a decision to be made accordingly. If you're in an area where there's lots of wildlife around, especially the aggressive / poisonous variety, then take extra care in watching where you're stepping. If you're in an area with lots of loose rocks, or an area with lots of rocks and it's been raining recently (potentially causing the ground beneath them to become unstable), then only step on rocks if you have to. Both of those are loose, rough rules, but hopefully get the right idea across.
Of course, the above only really applies if it's in an area with which you're already familiar - if in doubt, then I'll generally prefer to step on the rock, but only after putting my boot up against it first to check if it feels firm and not too slippery.
Both approaches have drawbacks, the key is knowing what those drawbacks are and thus being able to calculate for a given scenario what poses the least risk.
Stepping on a rock during a hike is always riskier than that of stepping "Over" a rock/log. I must have lost my footing a gazillion times trying to step "On" a rock. Regarding startling a snake/critter, most of the times, stepping on a rock "does not" guarantee that you are not going to startle the critter! So better step over a rock/log and prevent a roll down the hillside :D
The answer will vary depending on WHERE you are:
Desert: Lots of dry rock. Lots of ledges. Lots of snakes. Better to look before you leap over one. And, you get pretty good at judging which rocks might shift on you before you step on them. Lots of people I've hiked with have had their ankles narrowly missed by rattlers hiding under. I never plant my foot blindly.
Wet Forest: Lots of slippery logs. Lots of snakes. However, stepping on any log (and many rocks) will result in your feet squirting right off the top (slick) or punching though (rotten). When hiking in wet forests, I try to never step on a log, root, or rock unless I've tested it first. Nor do I blindly plant my foot on the back side of one. Go around, be cautious.
Temperate Forest: Lots of logs and rocks. Moderate amount of snakes. When dry, logs are usually fine to step on. When wet, they can be deadly. Know your area, judge the risk.
In general - chances are you are smart enough to judge whether a rock/log is large enough or stable enough to support you. If not, you'll learn quickly. So a blanket "never step on one" seems unfounded.
