I am most definitely not a tarp camper, not since many miserable sleepless nights in the military with a cold river running under my pup tent, but still, I agree, "no bug protection", no wind protection, etc.. are not problems with the tarp, they are problems inherent with tarp CAMPING. Along with blowing dust, blowing snow and ice, conductive, radiative, and convective heat loss, varmints like rats chewing your pack, and the previously mentioned flowing water. But I am digressing into a rant about tarps.. forgive me.
I would like to have had the silnylon tested for its water resistance. Nothing is waterPROOF, especially fabric. I've tested and seen some cheap silnylon such as in the SeaToSummit sacks leak at only a few inches of static water pressure. I think rain induces a dynamic pressure as Richard previously mentioned.