Well its the question whether to land attack or not to land attack. seafaring is pretty much an essential, but the real argument lies in whether a land attack would outweigh the benefits of early booming.
As I see it these are the most likely outcomes:
1: The attack fails, the boomer manages to hold them off, with a larger economy they manage to out-gather out-age and out-class their opponent...gg
2: It succeeds to the extent that it cuts up the boomers economy at least down to the size of the land attackers. In this case, the attacker has an established military base upon the boomers land as well as a matching economic strength, so the odds look in favor of the attacker, but it could still go either way.
3: It catches the boomer completely off-guard and massacres their villagers and buildings, a quick gg in favor of the attacker.
As far as I believe, the element of surprise is the key factor here. If the boomer knows that the attacker has put forwards on their island they're going to be able to easily fend off an attack (as long as theyre of equal skill level with the other player). On the contrary, if the attacker manages to slip onto the boomers island and they know nothing about it,then the attacker has a damn good chance of catching the boomer unawares and dealing them a crushing blow.
The question arises now, how can a boomer be sure that he hasn't got forwards planted upon his island?
As was usggested, towers. Too expensive in the early game to tower enough of the island to provide a secure section and also, as Duan mentioned, the towers sometimes don't respond as you would want towards villagers.
Other options for the boomer would be to keep a villager constantly scouting their island. Depending on the size of the map, this can be a more effective detector of enemy forwards and the more villagers you add to the constant search, the greater chance you have of finding your enemies actions.
This constant scouting comes, too, at the cost of as many villagers working power as you assign to scouting, meaning that if the other playing is booming without scouting their island on a regular basis, they have a gathering bonus which works against your favor.
This makes it a game of sacrifices--- do you go for tactical security in scouting the island or do you go for economic efficiency by assigning those villagers onto much-needed early-game resources.
Whats everyones opinion?