Explore your surroundings, take the Honor opener and destroy those barb camps that pop up. Barb camps always pop up with a land unit in them first, so you have a number of turns before they start spawning ships.
I was running Trireme patrols on the same coastline. Sure, Honor would help sometimes, although one of the two times I was plundered by a barbarian Galley that must have spawned on the other side of America (which I couldn't explore without Open Borders, which don't unlock until friggin' Civil Service). However, I think it's clear that a design goal of the game is that no single social policy is "required" to play the rest of the game adequately. I like that the trade route system buffs the Honor opener, which otherwise feels pretty weak for me. But I reject out of hand that Honor is the "expected" solution to protect trade routes. Surely there should be other ways.
People just want the bigger rewards of cargo ships vs caravans but they don't want to work for it.
That all I see. It's pretty typical in a gaming community, "give me this instant reward or I will quit". Next comes the threat, "if you don't do as I say, no one will buy it and the product will fail".
I know what you mean: people come on in here complaining, "I haven't adapted to the expansion's changes yet, waaaa." But reread my post. I got three Triremes to patrol a relatively tiny area of coast, and I still got bushwhacked twice. Now it's the Renaissance, and I've four Caravels, with both Great Lighthouse and the Exploration opener, and I'm protecting all five of my international sea trade routes.
But it's not FUN. It's TEDIOUS.
This discussion reminds me of the column written by Mark Rosewater, Lead Designer of Magic: the Gathering. Here's a sample column where he talks about common design mistakes, and I feel like several of them apply to the current trade route system.
http://www.wizards.com/Magic/Magazine/Article.aspx?x=mtgcom/daily/mr253
Mistake #1 Making The Audience Do Something They Dont Want To Do
You, the designer, can make the player do anything you want, but you cant make them enjoy it. A good designer makes the game fun because he lets the players essentially do what they want to do.
An example Rosewater gives from Magic: he designed Odyssey block, whose mechanics revolved around the graveyard. Often in Odyssey block, the "correct play" was to use some irrelevant ability like "Discard a card: this creature gains first strike until end of turn" just to get more cards into your graveyard, because you had some other ability like "Threshold -- If you have 7 or more cards in your graveyard, this creature gains +4/+4." But you know what Rosewater discovered? Players don't
enjoy discarding their cards to eke out some weird advantage. Players like to
play their cards!
Back to Brave New World. As a cautious player, I don't really
want to send my caravans and cargo ships into potentially hostile countries across hexes that I don't have visibility on. But the game gives me very strong incentives to do it. Can I really afford to choose 3 gold per turn with Tyre over 7 gold and 1 science per turn with Washington?
Mistake #2 Making The Audience Do Unnecessary Work
Patrolling my shipping lanes every turn is tedious. And most of the time, they don't get attacked, so it was unnecessary.
Mistake #3 Dont Put Things They Care About Out of Their Control
lankypeter made many helpful suggestions about ways to lower or mitigate the risk of international trade routes, which also makes it sound more fun. Thanks! But there's still a definite feeling of loss of control here. Maybe a barbarian camp will spawn along my trade route; maybe it won't. Maybe my cargo ship will be beyond closed borders when a barbarian Galley sails up; maybe it will be behind my Trireme. Maybe America will sink that barbarian Galley before it sails up to my cargo ship; maybe it won't. Maybe another nation will declare war on me who is close to a trade route I established 28 turns ago, or maybe they won't.