I have that brown/silver 10×12 from Walmart, and I love it...dont diss my baby, man!
Different strokes for different folks, i guess. i also own that very same 10' x 12' brown/silver Walmart tarp, and it is unquestionably what i would want if my uses included laying it on coal etc.- it is one sturdy motherfucker. But for hitching/bike-camping, it is overkill, and overweight. I just can't imagine carrying that thing around in a pack.
To be clear, i am
not recommending the ultra-light silnylon or cuben fiber tarps. Those won't stand up to much hard use, and are ridiculously expensive. They are very very light. Silnylon will stand up to harder use than the blue, and probably the green, Walmart tarps though, which shred easily, and develop leaks wherever they are folded. I have several semi disintegrated ones i can take pics of, if someone doubts this.
I buy new Walmart blue/green tarps for landscaping shit and covering things every year; my silnylon poncho is going strong in its 5th year, with one failed grommet.
But urethane coated nylon tarps are pretty sturdy stuff- Boy Scouts use poly-nylon tarps, and they are very hard on gear. So do many US special forces units. Definitely way lighter duty than the brown/silver Walmart tarp, but also a small fraction of the weight, which also means you can use lighter lines, stakes, and poles, saving even more weight. My urethane coated Hennessy hex tarp is also going strong in its fifth year, and looks brand new, despite frequent use.
And of course i am way more bourgeois than many here, but a 10' x 10' olive drab urethane coated nylon tarp with 16 tabs (and zero grommets) for $59 is pretty affordable, only $43 more than the brown silver 10' x 12', and so much lighter:
That $43 will seem like money well spent by the second mile of walking. As long as you don't have to lie on coal.