In response to the observed strategy: "Barcelona and Genova usually sell wood and iron to each others capital on turn two, get the 1000 ducet bonus and then economically dominate the rest the game. It's really useful to have enough money to immediately slap a fort on that gold or gems port in Africa early in the game."

We nearly always do that too, except on turn 1. Then on turn 2 Barcelona and Genoa are able to build a third boat before Turkey or Venice can (at least without crippling their treasuries). In the early to mid game, extra boats are where you get the value for your money. We virtually never buy forts -- No profit in it, and there's usually little conflict until the last two turns, by which point most valuable ports have enough of a garrison to be safe, fort or no fort. No one in our games would risk losing a ship (or even a handful of sailors) to fight for a port just to overcome a monopoly early in the game anyway. The more tempting targets in the early to mid game are the boats carrying gems or gold with only 2-3 sailors. I certainly won't attack your port with 5-6 guys (and a fort?!) if I can pirate your poorly defended ships. All the more reason to buy more ships early (rather than forts) -- I can send escorts with the really valuable shipments, I can use them offensively, I can hinder my enemies' movement, or I can blockade my own ports if I do actually think you might attack them.

I've probably only ever seen 2 or 3 forts bought, but on the other hand, we buy sailors as fast as we possibly can. By turn 7 or 8 (4-player game), we usually find that the sailors run out, and we will actually bid higher to go first so we get first dibs on buying the remaining sailors. (And yes, we do buy sailors only according to the limits imposed by the number of commodities in the warehouse. We have a bit of an arms race mentality -- There's pretty much always enough cash to buy all the sailors you're allowed to, and sailors are essentially power, so why not? The only time you might hold back a bit is if your budget is a bit tight for a new boat that you need.) Is this just us, or is this pretty much how it goes for everyone?