I've always avoided netting pockets on the outsides of backpacks, on the principle that they would snag or wear out --Has anyone had experience with this?

They're definitely fragile. I've got two on my new day hike pack, and I use them but treat them with kid gloves. They're great places to store a garbage bag or two, and I often slide the tip of my Mora sheath into after I clip it to a strap, ditto my Thermarest Z-seat etc... but I don't let them become high traffic areas or they're going to rip for sure, and because of that, I don't store anything important there.

not exactly, tho I have found the two mesh water bottle pockets on our packs tend to allow the water bottles to slip out if you aren't paying close attention ... simple solution to that was add a biner to the bottle and clip the biner to a solid attachment point on the pack, YMMV

While I do like mesh pockets for water bottles they do snag and tear easily. I have had them tear on shopping carts even. I had one pack that had drawstrings with cord locks on the mesh pockets, but that seems to be rare. Like the other person said, carabiners and attachment points work well for retention, but can get annoying when one needs to remove the bottle.

A Ray Jardin's misused idea. He designed packs (Go-Lite) that had a mesh pocket on the back where you could stow a wet tarp or rain gear to dry. Other pack makers picked up the look but not the function and added them on the sides and bottom where they wear out quickly.

I am currently trying to deal with the problem of water bottles falling out of net pockets.

My current solution is to have a small carabiner to clip onto the water bottle. This works in the sense that I don't loose the bottle.

The problem is that I store the backpack in the trunk of the car. Inevitably, BOTH water bottles work their way out of the net pocket. I would prefer to just grab and go when I need to use the backpack. Instead, I have to fish out the bottle out from under something, place them back in the pocket and go. Not as convenient as I would like.

I am thinking about experimenting with a bit of velcro on the mouth of the net pocket. Would sewing on an elastic band around the mouth of the pocket be a better choice?

I'm also a fan of clipping the water bottle in with a carabiner. I also have a couple of packs where the bottle holder zips completely shut.

it's another one of those "it depends" sort of deals.hiking out West on open trails it might work just fine.back in the woods with snags everywhere mesh would be a branch trap.
a real pocket can hold anything,mesh is a sieve.
like it has already been said,someone put mesh on a pack to dry clothes on the move and it became a icon of hard core outdoor gear and spun off everywhere.the mesh pocket and a clip to hold bottles is that belt and suspenders deal-----

What about lacing a shoelace around the opening, through the netting. Instant drawstring closure.

Great idea. I'm going to try it.

tnx.