Anyone who has bottles popping out seriously needs to rethink their choice in bottle cages.
I have a $12 specialized Rib Cage and I ride in NYC (can you say "conEd Crater"? I knew you could) and I've never had a bottle pop out with these cages. They're cheap. They're light. And they don't drop bottles.
Wire cages? Hey, no problem. Just don't ride around other people.
4gram carbon cages? Again, stick to time trials and stay away from any groups, especially any group I might be in.
Thank you.