WildPony
Warlord
Re: the Lighthouse...vs a strong human player: any ships you leave unprotected, at sea, are magnets for his navy. And stealing techs can be hazardous if the human player has a dip in said city, you use up your dip to steal the tech and the dip in the city buys your ship. Or a "bigger" ship pops out and sinks you. In addition, Magnatism comes along all too quickly to snuff out the Lamp.
One good thought for the Lighthouse, It can be beneficial to physically establish embassies with the AIs asap, rather than use MP and eventually lose out when MP expires. On the other hand, by the time MP expires, one should have the game well in hand and be able to establish new embassies if needed.
As for stealing techs, go for it. I like to keep a dip or two in reserve for those occasions, but if your using MP properly, you should have all the discovered techs. And in a game where your constantly expanding, ie., building new cities, and capturing/bribing enemy cities, this is a foregone conclusion.
Lighthouse for me is about totally dominating the sea primarily before Navigation and vs. a human enemy, not ai's and gaining a game winning advantage during that time... an advantage thru leveraging steals and super trade and forcing the enemy to defend every city that puts you in the drivers seat to get all or most other wonders you want including Magellans. Upon Navigation, the guy without the Lamp can then kill your vet triremes or vet caravels with non vet Caravels... u can still dominate, but not as completely as with vet triremes vs. non vet triremes. So the domination of which i speak all happens pre-navi while there are no bigger ships to sink yours... and let a man try sinking vet triremes with non vets. It's just plain ugly. As a rule, if i really want to sink a vet trireme (which i almost never want to do since it is so cost prohibitive) i have 3-4 non vets lined up in case the first 2-3 fail... which often they will.
The next level of domination Lighthouse can bring comes if you can reach Steam Engine before somebody else reaches Magnetism, but that won't happen very often vs. a strong human opponent.
Bribes i am not thinking about since most human games i have ever played have been 'no bribe", but in that case, yes, u want to keep your vet triremes "with occupant(s)" and your vet Iron Clads doubled up

Good point about using Lighthouse to help set up embassies to replace Marco's, but if it's 7 ai civ's, 4 caravans is cheaper than 7 dips, not to mention how much quicker and simpler it is. The fewer the number of enemies civs, the more sense physical embassies make over Marco's.