hey i haven't had time this monring to read the theories section, but i hope this isn't a repeat of another theory or that it doesn't seem like common sense...
anyway in last night's the Lighthouse brought us to just that, a lighthouse. i beleive jack says something along the lines of "how come we've never seen this?" to which hurley responds we just weren't looking for it. i am not sure who, i think maybe eloise, but somebody once said something like "you just have to know where to look" for the island.
that being said, i think it's the same general principle for the lighthouse. jacob had given hurley a pretty specific route, not just "go east until you see a giant lightouse past the trees" type directions. my theory is that you need to take a special path in order to find the lighthouse, starting from the temple.
jack, hurley, or any of the others survivors for that matter have never seen the lighthouse because it is hidden, unless you take the right path, or maybe hit the right bearing.
i'm just thinking, if you need an exact bearing to get to and from the island, who is to say that there aren't other hidden hot spots on the island.